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Sample records for auditory steady-state response

  1. Electrically Evoked Auditory Steady State Responses in Cochlear Implant Users

    PubMed Central

    Wouters, Jan

    2009-01-01

    Auditory steady state responses are neural potentials in response to repeated auditory stimuli. This study shows that electrically evoked auditory steady state responses (EASSRs) to low-rate pulse trains can be reliably recorded by electrodes placed on the scalp of a cochlear implant (CI) user and separated from the artifacts generated by the electrical stimulation. Response properties are described, and the predictive value of EASSRs for behaviorally hearing thresholds is analyzed. For six users of a Cochlear Nucleus CI, EASSRs to symmetric biphasic pulse trains with rates between 35 and 47 Hz were recorded with seven scalp electrodes. The influence of various stimulus parameters was assessed: pulse rate, stimulus intensity, monopolar or bipolar stimulation mode, and presentation of either one pulse train on one electrode or interleaved pulse trains with different pulse rates on multiple electrodes. To compensate for the electrical artifacts caused by the stimulus pulses and radio frequency transmission, different methods of artifact reduction were employed. The validity of the recorded responses was confirmed by recording on–off responses, determination of response latency across the measured pulse rates, and comparison of amplitude growth of stimulus artifact and response amplitude. For stimulation in the 40 Hz range, response latencies of 35.6 ms (SD = 5.3 ms) were obtained. Responses to multiple simultaneous stimuli on different electrodes can be evoked, and the electrophysiological thresholds determined from EASSR amplitude growth in the 40 Hz range correlate well with behaviorally determined threshold levels for pulse rates of 41 Hz. PMID:20033246

  2. [Auditory steady-state responses--the state of art].

    PubMed

    Szymańska, Anna; Gryczyński, Maciej; Pajor, Anna

    2010-01-01

    The auditory steady-state responses (ASSR) is quite a new method of electrophysiological threshold estimation with no clinical standards. It was the aim of this study to review practical and theoretical thesis of ASSR and mention recent recommendations and achievements of this technique. The most common application of ASSR is diagnosis of hearing loss in children together with ABR test. In this paper we mentioned information about influence of physiological factors (age, sex, state of arousal, handedness) and type of recording technique (electrodes placement, air and bone stimulation, occlusion effect, amplitude and frequency stimulation, multiple or single frequency stimulation, dichotic and monotic recording technique and type of hearing loss) on ASSR. We conclude that putting ASSR in clinical use as an standardized method it is necessary to do research with numerous groups of patients using the same equipment and parameters of tests. PMID:21166136

  3. Phencyclidine Disrupts the Auditory Steady State Response in Rats

    PubMed Central

    Leishman, Emma; O’Donnell, Brian F.; Millward, James B.; Vohs, Jenifer L.; Rass, Olga; Krishnan, Giri P.; Bolbecker, Amanda R.; Morzorati, Sandra L.

    2015-01-01

    The Auditory Steady-State Response (ASSR) in the electroencephalogram (EEG) is usually reduced in schizophrenia (SZ), particularly to 40 Hz stimulation. The gamma frequency ASSR deficit has been attributed to N-methyl-D-aspartate receptor (NMDAR) hypofunction. We tested whether the NMDAR antagonist, phencyclidine (PCP), produced similar ASSR deficits in rats. EEG was recorded from awake rats via intracranial electrodes overlaying the auditory cortex and at the vertex of the skull. ASSRs to click trains were recorded at 10, 20, 30, 40, 50, and 55 Hz and measured by ASSR Mean Power (MP) and Phase Locking Factor (PLF). In Experiment 1, the effect of different subcutaneous doses of PCP (1.0, 2.5 and 4.0 mg/kg) on the ASSR in 12 rats was assessed. In Experiment 2, ASSRs were compared in PCP treated rats and control rats at baseline, after acute injection (5 mg/kg), following two weeks of subchronic, continuous administration (5 mg/kg/day), and one week after drug cessation. Acute administration of PCP increased PLF and MP at frequencies of stimulation below 50 Hz, and decreased responses at higher frequencies at the auditory cortex site. Acute administration had a less pronounced effect at the vertex site, with a reduction of either PLF or MP observed at frequencies above 20 Hz. Acute effects increased in magnitude with higher doses of PCP. Consistent effects were not observed after subchronic PCP administration. These data indicate that acute administration of PCP, a NMDAR antagonist, produces an increase in ASSR synchrony and power at low frequencies of stimulation and a reduction of high frequency (> 40 Hz) ASSR activity in rats. Subchronic, continuous administration of PCP, on the other hand, has little impact on ASSRs. Thus, while ASSRs are highly sensitive to NMDAR antagonists, their translational utility as a cross-species biomarker for NMDAR hypofunction in SZ and other disorders may be dependent on dose and schedule. PMID:26258486

  4. 40 Hz auditory steady state response to linguistic features of stimuli during auditory hallucinations.

    PubMed

    Ying, Jun; Yan, Zheng; Gao, Xiao-rong

    2013-10-01

    The auditory steady state response (ASSR) may reflect activity from different regions of the brain, depending on the modulation frequency used. In general, responses induced by low rates (≤40 Hz) emanate mostly from central structures of the brain, and responses from high rates (≥80 Hz) emanate mostly from the peripheral auditory nerve or brainstem structures. Besides, it was reported that the gamma band ASSR (30-90 Hz) played an important role in working memory, speech understanding and recognition. This paper investigated the 40 Hz ASSR evoked by modulated speech and reversed speech. The speech was Chinese phrase voice, and the noise-like reversed speech was obtained by temporally reversing the speech. Both auditory stimuli were modulated with a frequency of 40 Hz. Ten healthy subjects and 5 patients with hallucination symptom participated in the experiment. Results showed reduction in left auditory cortex response when healthy subjects listened to the reversed speech compared with the speech. In contrast, when the patients who experienced auditory hallucinations listened to the reversed speech, the auditory cortex of left hemispheric responded more actively. The ASSR results were consistent with the behavior results of patients. Therefore, the gamma band ASSR is expected to be helpful for rapid and objective diagnosis of hallucination in clinic. PMID:24142731

  5. Evidence against attentional state modulating scalp-recorded auditory brainstem steady-state responses.

    PubMed

    Varghese, Leonard; Bharadwaj, Hari M; Shinn-Cunningham, Barbara G

    2015-11-11

    Auditory brainstem responses (ABRs) and their steady-state counterpart (subcortical steady-state responses, SSSRs) are generally thought to be insensitive to cognitive demands. However, a handful of studies report that SSSRs are modulated depending on the subject׳s focus of attention, either towards or away from an auditory stimulus. Here, we explored whether attentional focus affects the envelope-following response (EFR), which is a particular kind of SSSR, and if so, whether the effects are specific to which sound elements in a sound mixture a subject is attending (selective auditory attentional modulation), specific to attended sensory input (inter-modal attentional modulation), or insensitive to attentional focus. We compared the strength of EFR-stimulus phase locking in human listeners under various tasks: listening to a monaural stimulus, selectively attending to a particular ear during dichotic stimulus presentation, and attending to visual stimuli while ignoring dichotic auditory inputs. We observed no systematic changes in the EFR across experimental manipulations, even though cortical EEG revealed attention-related modulations of alpha activity during the task. We conclude that attentional effects, if any, on human subcortical representation of sounds cannot be observed robustly using EFRs. This article is part of a Special Issue entitled SI: Prediction and Attention. PMID:26187756

  6. Improving auditory steady-state response detection using independent component analysis on multichannel EEG data.

    PubMed

    Van Dun, Bram; Wouters, Jan; Moonen, Marc

    2007-07-01

    Over the last decade, the detection of auditory steady-state responses (ASSR) has been developed for reliable hearing threshold estimation at audiometric frequencies. Unfortunately, the duration of ASSR measurement can be long, which is unpractical for wide scale clinical application. In this paper, we propose independent component analysis (ICA) as a tool to improve the ASSR detection in recorded single-channel as well as multichannel electroencephalogram (EEG) data. We conclude that ICA is able to reduce measurement duration significantly. For a multichannel implementation, near-optimal performance is obtained with five-channel recordings. PMID:17605353

  7. Cholinergic modulation of auditory steady-state response in the auditory cortex of the freely moving rat.

    PubMed

    Zhang, J; Ma, L; Li, W; Yang, P; Qin, L

    2016-06-01

    As disturbance in auditory steady-state response (ASSR) has been consistently found in many neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia, there is considerable interest in the development of translational rat models to elucidate the underlying neural and neurochemical mechanisms involved in ASSR. This is the first study to investigate the effects of the non-selective muscarinic antagonist scopolamine and the cholinesterase inhibitor donepezil (also in combination with scopolamine) on ASSR. We recorded the local field potentials through the chronic microelectrodes implanted in the auditory cortex of freely moving rat. ASSRs were recorded in response to auditory stimuli delivered over a range of frequencies (10-80Hz) and averaged over 60 trials. We found that a single dose of scopolamine produced a temporal attenuation in response to auditory stimuli; the most attenuation occurred at 40Hz. Time-frequency analysis revealed deficits in both power and phase-locking to 40Hz. Donepezil augmented 40-Hz steady-state power and phase-locking. Scopolamine combined with donepezil had an enhanced effect on the phase-locking, but not power of ASSR. These changes induced by cholinergic drugs suggest an involvement of muscarinic neurotransmission in auditory processing and provide a rodent model investigating the neurochemical mechanism of neurophysiological deficits seen in patients. PMID:26964684

  8. The effect of the transducers on paediatric thresholds estimated with auditory steady-state responses.

    PubMed

    Bakhos, D; Vitaux, H; Villeneuve, A; Kim, S; Lescanne, E; Pigeon, V; Aoustin, J M; Bordure, P; Galvin, J

    2016-08-01

    The objective of this study was to investigate the usefulness of auditory steady-state responses (ASSRs) for estimating hearing thresholds in young children, compared with behavioural thresholds. The second objective was to investigate ASSR thresholds obtained with insert earphones versus supra-aural headphones to determine which transducer produces ASSR thresholds most similar to behavioural thresholds measured with supra-aural headphones. This retrospective study included 29 participants (58 ears): 12 children (24 ears) in the insert group and 17 children (34 ears) in the supra-aural group. No general anaesthesia was used. For both groups, there was a strong correlation between behavioural and ASSR thresholds, with a stronger correlation for the insert group. When behavioural thresholds are difficult to obtain, ASSR may be a useful objective measure that can be combined with other audiometric procedures to estimate hearing thresholds and to determine appropriate auditory rehabilitation approaches. PMID:26329899

  9. Can place-specific cochlear dispersion be represented by auditory steady-state responses?

    PubMed

    Paredes Gallardo, Andreu; Epp, Bastian; Dau, Torsten

    2016-05-01

    The present study investigated to what extent properties of local cochlear dispersion can be objectively assessed through auditory steady-state responses (ASSR). The hypothesis was that stimuli compensating for the phase response at a particular cochlear location generate a maximally modulated basilar membrane (BM) response at that BM position, due to the large "within-channel" synchrony of activity. This would lead, in turn, to a larger ASSR amplitude than other stimuli of corresponding intensity and bandwidth. Two stimulus types were chosen: 1] Harmonic tone complexes consisting of equal-amplitude tones with a starting phase following an algorithm developed by Schroeder [IEEE Trans. Inf. Theory 16, 85-89 (1970)] that have earlier been considered in behavioral studies to estimate human auditory filter phase responses; and 2] simulations of auditory-filter impulse responses (IR). In both cases, also the temporally reversed versions of the stimuli were considered. The ASSRs obtained with the Schroeder tone complexes were found to be dominated by "across-channel" synchrony and, thus, do not reflect local place-specific information. In the case of the more frequency-specific stimuli, no significant differences were found between the responses to the IR and its temporally reversed counterpart. Thus, whereas ASSRs to narrowband stimuli have been used as an objective indicator of frequency-specific hearing sensitivity, the method does not seem to be sensitive enough to reflect local cochlear dispersion. PMID:26906677

  10. Deficits in the 30-Hz auditory steady-state response in patients with major depressive disorder.

    PubMed

    Chen, Jingjing; Gong, Qin; Wu, Fei

    2016-10-19

    The auditory steady-state response (ASSR) is an auditory evoked potential that occurs in response to periodically presented auditory stimuli. The ASSR has drawn attention as a biomarker of psychiatric disorders owing to its connection with neural oscillations as well as its easy and noninvasive recording. Abnormalities in the γ band ASSR have been found consistently in patients with schizophrenia and bipolar disorder. However, although major depressive disorder (MDD) is also part of the common psychiatric diseases, the relationship between the ASSR and MDD has not been characterized sufficiently. Thus, the aim of the present study was to examine the ASSRs from patients with MDD and compare them with those from healthy control (HC) participants. The experiment was designed to obtain the ASSRs elicited by 20-, 30-, and 40-Hz click trains. Patients and HCs were evaluated separately. The response power and phase synchronization were measured at each stimulation frequency. Patients with MDD showed significantly reduced ASSR power for 30-Hz stimuli compared with HC participants, whereas no significant differences in the power were observed at 20 and 40 Hz for patients with MDD. In addition, no significant difference in the phase synchronization was observed for 20-, 30-, and 40-Hz stimuli. Conclusively, patients with MDD were characterized by deficits in 30-Hz ASSR power, which may be associated with spontaneous γ activity dysfunction. The present findings suggest that ASSR could potentially be used as a biomarker for MDD. PMID:27563737

  11. Rapid acquisition of auditory subcortical steady state responses using multichannel recordings✩

    PubMed Central

    Bharadwaj, Hari M.; Shinn-Cunningham, Barbara G.

    2015-01-01

    Objective Auditory subcortical steady state responses (SSSRs), also known as frequency following responses (FFRs), provide a non-invasive measure of phase-locked neural responses to acoustic and cochlear-induced periodicities. SSSRs have been used both clinically and in basic neurophysiological investigation of auditory function. SSSR data acquisition typically involves thousands of presentations of each stimulus type, sometimes in two polarities, with acquisition times often exceeding an hour per subject. Here, we present a novel approach to reduce the data acquisition times significantly. Methods Because the sources of the SSSR are deep compared to the primary noise sources, namely background spontaneous cortical activity, the SSSR varies more smoothly over the scalp than the noise. We exploit this property and extract SSSRs efficiently, using multichannel recordings and an eigendecomposition of the complex cross-channel spectral density matrix. Results Our proposed method yields SNR improvement exceeding a factor of 3 compared to traditional single-channel methods. Conclusions It is possible to reduce data acquisition times for SSSRs significantly with our approach. Significance The proposed method allows SSSRs to be recorded for several stimulus conditions within a single session and also makes it possible to acquire both SSSRs and cortical EEG responses without increasing the session length. PMID:24525091

  12. Auditory steady state response in hearing assessment in infants with cytomegalovirus

    PubMed Central

    Silva, Daniela Polo C.; Lopez, Priscila Suman; Montovani, Jair Cortez

    2013-01-01

    OBJECTIVE: To report an infant with congenital cytomegalovirus and progressive sensorineural hearing loss, who was assessed by three methods of hearing evaluation. CASE DESCRIPTION: In the first audiometry, at four months of age, the infant showed abnormal response in Otoacoustic Emissions and normal Auditory Brainstem Response (ABR), with electrophysiological threshold in 30dBnHL, in both ears. With six months of age, he showed bilateral absence of the ABR at 100dBnHL. The behavioral observational audiometry was impaired due to the delay in neuropsychomotor development. At eight months of age, he was submitted to Auditory Steady State Response (ASSR) and the thresholds were 50, 70, absent in 110 and in 100dB, respectively for 500, 1,000, 2,000 and 4,000Hz in the right ear, and 70, 90, 90 and absent in 100dB, respectively for 500, 1,000, 2,000 and 4,000Hz in the left ear. COMMENTS: In the first evaluation, the infant had abnormal Otoacoustic Emission and normal ABR, which became altered at six months of age. The hearing loss severity could be identified only by the ASSR, which allowed the best procedure for hearing aids adaptation. The case description highlights the importance of the hearing status follow-up for children with congenital cytomegalovirus. PMID:24473963

  13. 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

  14. Brain-computer interfaces using capacitive measurement of visual or auditory steady-state responses

    NASA Astrophysics Data System (ADS)

    Baek, Hyun Jae; Kim, Hyun Seok; Heo, Jeong; Lim, Yong Gyu; Park, Kwang Suk

    2013-04-01

    Objective. Brain-computer interface (BCI) technologies have been intensely studied to provide alternative communication tools entirely independent of neuromuscular activities. Current BCI technologies use electroencephalogram (EEG) acquisition methods that require unpleasant gel injections, impractical preparations and clean-up procedures. The next generation of BCI technologies requires practical, user-friendly, nonintrusive EEG platforms in order to facilitate the application of laboratory work in real-world settings. Approach. A capacitive electrode that does not require an electrolytic gel or direct electrode-scalp contact is a potential alternative to the conventional wet electrode in future BCI systems. We have proposed a new capacitive EEG electrode that contains a conductive polymer-sensing surface, which enhances electrode performance. This paper presents results from five subjects who exhibited visual or auditory steady-state responses according to BCI using these new capacitive electrodes. The steady-state visual evoked potential (SSVEP) spelling system and the auditory steady-state response (ASSR) binary decision system were employed. Main results. Offline tests demonstrated BCI performance high enough to be used in a BCI system (accuracy: 95.2%, ITR: 19.91 bpm for SSVEP BCI (6 s), accuracy: 82.6%, ITR: 1.48 bpm for ASSR BCI (14 s)) with the analysis time being slightly longer than that when wet electrodes were employed with the same BCI system (accuracy: 91.2%, ITR: 25.79 bpm for SSVEP BCI (4 s), accuracy: 81.3%, ITR: 1.57 bpm for ASSR BCI (12 s)). Subjects performed online BCI under the SSVEP paradigm in copy spelling mode and under the ASSR paradigm in selective attention mode with a mean information transfer rate (ITR) of 17.78 ± 2.08 and 0.7 ± 0.24 bpm, respectively. Significance. The results of these experiments demonstrate the feasibility of using our capacitive EEG electrode in BCI systems. This capacitive electrode may become a flexible and

  15. The 40-Hz auditory steady-state response: a selective biomarker for cortical NMDA function.

    PubMed

    Sivarao, Digavalli V

    2015-05-01

    When subjected to a phasic input, sensory cortical neurons display a remarkable ability to entrain faithfully to the driving stimuli. The entrainment to rhythmic sound stimuli is often referred to as the auditory steady-state response (ASSR) and can be captured using noninvasive techniques, such as scalp-recorded electroencephalography (EEG). An ASSR to a driving frequency of approximately 40 Hz is particularly interesting in that it shows, in relative terms, maximal power, synchrony, and synaptic activity. Moreover, the 40-Hz ASSR has been consistently found to be abnormal in schizophrenia patients across multiple studies. The nature of the reported abnormality has been less consistent; while most studies report a deficit in entrainment, several studies have reported increased signal power, particularly when there are concurrent positive symptoms, such as auditory hallucinations. However, the neuropharmacological basis for the 40-Hz ASSR, as well as its dysfunction in schizophrenia, has been unclear until recently. On the basis of several recent reports, it is argued that the 40-Hz ASSR represents a specific marker for cortical NMDA transmission. If confirmed, the 40-Hz ASSR may be a simple and easy-to-access pharmacodynamic biomarker for testing the integrity of cortical NMDA neurotransmission that is robustly translational across species. PMID:25809615

  16. Auditory steady-state responses in cochlear implant users: Effect of modulation frequency and stimulation artifacts.

    PubMed

    Gransier, Robin; Deprez, Hanne; Hofmann, Michael; Moonen, Marc; van Wieringen, Astrid; Wouters, Jan

    2016-05-01

    Previous studies have shown that objective measures based on stimulation with low-rate pulse trains fail to predict the threshold levels of cochlear implant (CI) users for high-rate pulse trains, as used in clinical devices. Electrically evoked auditory steady-state responses (EASSRs) can be elicited by modulated high-rate pulse trains, and can potentially be used to objectively determine threshold levels of CI users. The responsiveness of the auditory pathway of profoundly hearing-impaired CI users to modulation frequencies is, however, not known. In the present study we investigated the responsiveness of the auditory pathway of CI users to a monopolar 500 pulses per second (pps) pulse train modulated between 1 and 100 Hz. EASSRs to forty-three modulation frequencies, elicited at the subject's maximum comfort level, were recorded by means of electroencephalography. Stimulation artifacts were removed by a linear interpolation between a pre- and post-stimulus sample (i.e., blanking). The phase delay across modulation frequencies was used to differentiate between the neural response and a possible residual stimulation artifact after blanking. Stimulation artifacts were longer than the inter-pulse interval of the 500pps pulse train for recording electrodes ipsilateral to the CI. As a result the stimulation artifacts could not be removed by artifact removal on the bases of linear interpolation for recording electrodes ipsilateral to the CI. However, artifact-free responses could be obtained in all subjects from recording electrodes contralateral to the CI, when subject specific reference electrodes (Cz or Fpz) were used. EASSRs to modulation frequencies within the 30-50 Hz range resulted in significant responses in all subjects. Only a small number of significant responses could be obtained, during a measurement period of 5 min, that originate from the brain stem (i.e., modulation frequencies in the 80-100 Hz range). This reduced synchronized activity of brain stem

  17. Auditory steady state responses in a schizophrenia rat model probed by excitatory/inhibitory receptor manipulation

    PubMed Central

    Vohs, Jenifer L.; Chambers, R. Andrew; O’Donnell, Brian F.; Krishnan, Giri P.; Morzorati, Sandra L.

    2012-01-01

    Alterations in neural synchrony and oscillations may contribute to the pathophysiology of schizophrenia and reflect aberrations in cortical glutamatergic and GABAergic neurotransmission. We tested the effects of a GABA agonist and a NMDA antagonist on auditory steady state responses (ASSRs) in awake rats with neonatal ventral hippocampal lesions (NVHLs) as a neurodevelopmental model of schizophrenia. NVHL vs. SHAM lesioned rats were injected with saline then either ketamine (NMDA antagonist) or muscimol (GABAA agonist). Time-frequency analyses examined alterations in phase locking (consistency) across trials and changes in total power (magnitude). ASSRs were compared at 5 stimulation frequencies (10, 20, 30, 40, and 50 Hz). In SHAM rats, phase locking and power generally increased with stimulation frequency. Both ketamine and muscimol also increased phase locking and power in SHAM rats, but mostly in the 20 to 40 Hz range. NVHL and ketamine altered the frequency dependence of phase locking, while only ketamine changed power frequency dependence. Muscimol affected power, but not phase locking, in the NVHL rats. NVHL and ketamine models of schizophrenia produce similar independent effects on ASSR, potentially representing similar forms of cortical network/glutamatergic dysfunction, albeit the effects of ketamine were more robust. Muscimol produced NVHL-dependent reductions in ASSR measures, suggesting that cortical networks in this model are intolerant to post-synaptic GABAergic stimulation. These findings suggest the utility of combining lesion, pharmacological, and ASSR approaches in understanding neural mechanisms underlying disturbed synchrony in schizophrenia. PMID:22504207

  18. Improved electrically evoked auditory steady-state response thresholds in humans.

    PubMed

    Hofmann, Michael; Wouters, Jan

    2012-08-01

    Electrically evoked auditory steady-state responses (EASSRs) are EEG potentials in response to periodic electrical stimuli presented through a cochlear implant. For low-rate pulse trains in the 40-Hz range, electrophysiological thresholds derived from response amplitude growth functions correlate well with behavioral T levels at these rates. The aims of this study were: (1) to improve the correlation between electrophysiological thresholds and behavioral T levels at 900 pps by using amplitude-modulated (AM) and pulse-width-modulated (PWM) high-rate pulse trains, (2) to develop and evaluate the performance of a new statistical method for response detection which is robust in the presence of stimulus artifacts, and (3) to assess the ability of this statistical method to determine reliable electrophysiological thresholds without any stimulus artifact removal. For six users of a Nucleus cochlear implant and a total of 12 stimulation electrode pairs, EASSRs to symmetric biphasic bipolar pulse trains were recorded with seven scalp electrodes. Responses to six different stimuli were analyzed: two low-rate pulse trains with pulse rates in the 40-Hz range as well as two AM and two PWM high-rate pulse trains with a carrier rate of 900 pps and modulation frequencies in the 40-Hz range. Responses were measured at eight different stimulus intensities for each stimulus and stimulation electrode pair. Artifacts due to the electrical stimulation were removed from the recordings. To determine the presence of a neural response, a new statistical method based on a two-sample Hotelling T (2) test was used. Measurements from different recording electrodes and adjacent stimulus intensities were combined to increase statistical power. The results show that EASSRs to modulated high-rate pulse trains account for some of the temporal effects at 900 pps and result in improved electrophysiological thresholds that correlate very well with behavioral T levels at 900 pps. The proposed

  19. Using the auditory steady-state response to assess temporal dynamics of hearing sensitivity during bottlenose dolphin echolocation.

    PubMed

    Finneran, James J; Mulsow, Jason; Houser, Dorian S

    2013-11-01

    The auditory steady-state response (ASSR) to an external tone was measured in an echolocating dolphin to determine if hearing sensitivity changes could be tracked over time scales corresponding to single click-echo pairs. Individual epochs containing click-echo pairs were first extracted from the instantaneous electroencephalogram. Epochs were coherently averaged using the external tone modulation rate as a timing reference, then Fourier transformed using a sliding, 10-ms temporal window to obtain the ASSR amplitude as a function of time. The results revealed a decrease in the ASSR amplitude at the time of click emission, followed by a 25-70 ms recovery. PMID:24180800

  20. 40 Hz Auditory Steady-State Response Is a Pharmacodynamic Biomarker for Cortical NMDA Receptors.

    PubMed

    Sivarao, Digavalli V; Chen, Ping; Senapati, Arun; Yang, Yili; Fernandes, Alda; Benitex, Yulia; Whiterock, Valerie; Li, Yu-Wen; Ahlijanian, Michael K

    2016-08-01

    Schizophrenia patients exhibit dysfunctional gamma oscillations in response to simple auditory stimuli or more complex cognitive tasks, a phenomenon explained by reduced NMDA transmission within inhibitory/excitatory cortical networks. Indeed, a simple steady-state auditory click stimulation paradigm at gamma frequency (~40 Hz) has been reproducibly shown to reduce entrainment as measured by electroencephalography (EEG) in patients. However, some investigators have reported increased phase locking factor (PLF) and power in response to 40 Hz auditory stimulus in patients. Interestingly, preclinical literature also reflects this contradiction. We investigated whether a graded deficiency in NMDA transmission can account for such disparate findings by administering subanesthetic ketamine (1-30 mg/kg, i.v.) or vehicle to conscious rats (n=12) and testing their EEG entrainment to 40 Hz click stimuli at various time points (~7-62 min after treatment). In separate cohorts, we examined in vivo NMDA channel occupancy and tissue exposure to contextualize ketamine effects. We report a robust inverse relationship between PLF and NMDA occupancy 7 min after dosing. Moreover, ketamine could produce inhibition or disinhibition of the 40 Hz response in a temporally dynamic manner. These results provide for the first time empirical data to understand how cortical NMDA transmission deficit may lead to opposite modulation of the auditory steady-state response (ASSR). Importantly, our findings posit that 40 Hz ASSR is a pharmacodynamic biomarker for cortical NMDA function that is also robustly translatable. Besides schizophrenia, such a functional biomarker may be of value to neuropsychiatric disorders like bipolar and autism spectrum where 40 Hz ASSR deficits have been documented. PMID:26837462

  1. Are Auditory Steady-State Responses Useful to Evaluate Severe-to-Profound Hearing Loss in Children?

    PubMed Central

    Grasel, Signe Schuster; de Almeida, Edigar Rezende; Beck, Roberto Miquelino de Oliveira; Goffi-Gomez, Maria Valéria Schmidt; Ramos, Henrique Faria; Rossi, Amanda Costa; Koji Tsuji, Robinson; Bento, Ricardo Ferreira; de Brito, Rubens

    2015-01-01

    Objective. To evaluate Auditory Steady-State Responses (ASSR) at high intensities in pediatric cochlear implant candidates and to compare the results to behavioral tests responses. Methods. This prospective study evaluated 42 children with suspected severe-to-profound hearing loss, aged from 3 to 72 months. All had absent ABR and OAE responses. ASSR were evoked using binaural single frequency stimuli at 110 dB HL with a 10 dB down-seeking procedure. ASSR and behavioral test results were compared. Results. Forty-two subjects completed both ASSR and behavioral evaluation. Eleven children (26.2%) had bilateral responses. Four (9.5%) showed unilateral responses in at least two frequencies, all confirmed by behavioral results. Overall 61 ASSR responses were obtained, most (37.7%) in 500 Hz. Mean thresholds were between 101.3 and 104.2 dB HL. Among 27 subjects with absent ASSR, fifteen had no behavioral responses. Seven subjects showed behavioral responses with absent ASSR responses. No spurious ASSR responses were observed at 100 or 110 dB HL. Conclusion. ASSR is a valuable tool to detect residual hearing. No false-positive ASSR results were observed among 42 children, but in seven cases with absent ASSR, the test underestimated residual hearing as compared to the behavioral responses. PMID:26557677

  2. Avoiding spectral leakage in objective detection of auditory steady-state evoked responses in the inferior colliculus of rat using coherence.

    PubMed

    Felix, Leonardo Bonato; Moraes, José Elvano; Miranda de Sá, Antonio Mauricio Ferreira Leite; Yehia, Hani Camille; Moraes, Márcio Flávio Dutra

    2005-06-15

    Local field potentials (LFP) are bioelectric signals recorded from the brain that reflect neural activity in a high temporal resolution. Separating background activity from that evoked by specific somato-sensory input is a matter of great clinical relevance in neurology. The coherence function is a spectral coefficient that can be used as a detector of periodic responses in noisy environments. Auditory steady-state responses to amplitude-modulated tones generate periodic responses in neural networks that may be accessed by means of coherence between the stimulation signal and the LFP recorded from the auditory pathway. Such signal processing methodology was applied in this work to evaluate in vivo, anaesthetized Wistar rats, activation of neural networks due to single carrier sound stimulation frequencies, as well as to evaluate the effect of different modulating tones in the evoked responses. Our results show that an inappropriate choice of sound stimuli modulating frequencies can compromise coherence analysis, e.g. misleading conclusions due to mathematical artefact of signal processing. Two modulating frequency correction protocols were used: nearest integer and nearest prime number. The nearest prime number correction was successful in avoiding spectral leakage in the coherence analysis of steady-state auditory response, as predicted by Monte Carlo simulations. PMID:15910985

  3. Phase coherence of auditory steady-state response reflects the amount of cognitive workload in a modified N-back task.

    PubMed

    Yokota, Yusuke; Naruse, Yasushi

    2015-11-01

    The auditory steady-state response (ASSR) is an oscillatory brain activity evoked by repetitive auditory stimuli. Previous studies have reported that the power and phase locking index (PLI) of ASSR could be modulated by the degree of workload. However, those studies used different physical stimuli for tasks of differing difficulty, and the effect of the internal workload itself has not been clearly understood. In this study, we employed the modified N-back task as a visual working memory task in order to vary the degree of difficulty while keeping the physical stimulus constant. The experiment consisted of four types of tasks: No-Load (NL), 1-back, 2-back, and 3-back tasks. The auditory stimulus was a 40 Hz click sound to induce ASSR. Sixteen healthy subjects participated in the present study and magnetoencephalogram responses were recorded using a 148-channel magnetometer system. The hit rate decreased and the reaction time increased according to the task difficulty. Grand averaged phase coherence activities showed the 40 Hz ASSR reductions accompanying an increase in the task difficulty even with the identical external stimuli. In particular, the phase coherence activities in 3-back task were significantly lower than that in the NL and 1-back tasks. Our results suggest that the ASSR can be a useful indicator for the amount of workload in the brain. PMID:26149892

  4. Assessment of low-frequency hearing with narrow-band chirp-evoked 40-Hz sinusoidal auditory steady-state response.

    PubMed

    Wilson, Uzma S; Kaf, Wafaa A; Danesh, Ali A; Lichtenhan, Jeffery T

    2016-01-01

    Objective To determine the clinical utility of narrow-band chirp-evoked 40-Hz sinusoidal auditory steady state responses (s-ASSR) in the assessment of low-frequency hearing in noisy participants. Design Tone bursts and narrow-band chirps were used to respectively evoke auditory brainstem responses (tb-ABR) and 40-Hz s-ASSR thresholds with the Kalman-weighted filtering technique and were compared to behavioral thresholds at 500, 2000, and 4000 Hz. A repeated measure ANOVA and post-hoc t-tests, and simple regression analyses were performed for each of the three stimulus frequencies. Study sample Thirty young adults aged 18-25 with normal hearing participated in this study. Results When 4000 equivalent response averages were used, the range of mean s-ASSR thresholds from 500, 2000, and 4000 Hz were 17-22 dB lower (better) than when 2000 averages were used. The range of mean tb-ABR thresholds were lower by 11-15 dB for 2000 and 4000 Hz when twice as many equivalent response averages were used, while mean tb-ABR thresholds for 500 Hz were indistinguishable regardless of additional response averaging. Conclusion Narrow-band chirp-evoked 40-Hz s-ASSR requires a ∼15 dB smaller correction factor than tb-ABR for estimating low-frequency auditory threshold in noisy participants when adequate response averaging is used. PMID:26795555

  5. Effect of attention on 40Hz auditory steady-state response depends on the stimulation type: Flutter amplitude modulated tones versus clicks.

    PubMed

    Voicikas, Aleksandras; Niciute, Ieva; Ruksenas, Osvaldas; Griskova-Bulanova, Inga

    2016-08-26

    Auditory steady-state responses (ASSRs) are used to test the ability of local cortical networks to generate gamma frequency activity in patients with psychiatric disorders. For the effective use of ASSRs in research and clinical applications, it is necessary to find a comfortable stimulation type and to know how ASSRs are modulated by the tasks given to the subjects during the recording session. We aimed to evaluate the suitability of flutter amplitude modulated tone (FAM) stimulation for generation of ASSRs: subjective pleasantness of FAMs and attentional effects on FAM-elicited 40Hz ASSRs were assessed. Commonly used click stimulation was used for comparison. FAMs produced ASSRs that were stable over the variety of tasks - they were not modulated by attentional demands during the task; responses to clicks were reduced and less synchronized during distraction. FAM stimuli were rated as less unpleasant and less arousing than click stimuli, thus being more pleasant to the subjects. Our findings suggest that FAM stimulation might be more suitable in conditions, where attention is difficult to control, i.e. in clinical settings. PMID:27424792

  6. Steady state response of unsymmetrically laminated plates

    SciTech Connect

    Hosokawa, Kenji; Kawashima, Katsuya; Sakata, Toshiyuki

    1995-11-01

    A numerical approach for analyzing the forced vibration problem of a symmetrically laminated FRP (fiber reinforced plastic) composite plate was proposed by the authors. In the present paper, this approach is modified for application to an unsymmetrically laminated FRP composite plate. Numerical calculations are carried out for the clamped antisymmetrically laminated rectangular and elliptical plates which are a kind of unsymmetrically laminated plate. Then,, the effects of the lamina material and the fiber orientation angle on the steady state response are discussed. Furthermore, it is investigated that what structural damping factor is most influenced on the steady state response of an antisymmetrically laminated plate.

  7. Phase-locking index and power of 40-Hz auditory steady-state response are not related to major personality trait dimensions.

    PubMed

    Korostenskaja, Milena; Ruksenas, Osvaldas; Pipinis, Evaldas; Griskova-Bulanova, Inga

    2016-03-01

    Although a number of studies have demonstrated state-related dependence of auditory steady-state responses (ASSRs), the investigations assessing trait-related ASSR changes are limited. Five consistently identified major trait dimensions, also referred to as "big five" (Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness), are considered to account for virtually all personality variances in both healthy people and those with psychiatric disorders. The purpose of the present study was, for the first time, to establish the link between 40-Hz ASSR and "big five" major personality trait dimensions in young healthy adults. Ninety-four young healthy volunteers participated (38 males and 56 females; mean age ± SD 22.180 ± 2.75). The 40-Hz click trains were presented for each subject 30 times with an inter-train interval of 1-1.5 s. The EEG responses were recorded from F3, Fz, F4, C3, Cz, C4, P3, Pz and P4 locations according to 10/20 electrode placement system. Phase-locking index (PLI) and event-related power perturbation (ERSP) were calculated, each providing the following characteristics: peak time, entrainment frequency, peak value and mean value. For assessing "big five" personality traits, NEO Personality Inventory Revised (NEO-PI-R) was used. No significant correlation between 40-Hz ASSR PLI or ERSP and "big five" personality traits was observed. Our results indicate that there is no dependence between 40-Hz ASSR entrainment and personality traits, demonstrating low individual 40-Hz variability in this domain. Our results support further development of 40-Hz ASSR as a neurophysiological marker allowing distinguishing between healthy population and patients with psychiatric disorders. PMID:26586270

  8. [The evaluation of the hearing function in the premature infants with intrauterine growth retardation during the third and sixth months of life by recording auditory steady-state response].

    PubMed

    Rakhmanova, I V; D'yakonova, I N; Sichinava, L G; Ledovskikh, Yu A

    2015-01-01

    The objective of the present work was to study the function of the retrocochlear auditory pathway in the premature infants with intrauterine growth retardation (IGR) in comparison to that of the normotrophics of a similar gestational age during the third and sixth months of life by recording auditory steady-state responses (ASSR). The audiological examination by the method of auditory steady-state response (ASSR) involved 127 children at the 3d month of life and in 97 children at the 6th month of life. It was shown that the ASSR thresholds at certain frequencies during the 3d and 6th months of life of the children born after the 32d week of pregnancy were significantly higher than in the children born after 32 weeks gestation. The comparison of the two objective audiological methods, viz. distortion-product otoacoustic emission (DPOAE) and ASSR, indicates that both should be used to evaluate the hearing function during the third and sixth months of life to compensate for the discrepancy between the results obtained by either technique. PMID:26978745

  9. Estimation of the reaction times in tasks of varying difficulty from the phase coherence of the auditory steady-state response using the least absolute shrinkage and selection operator analysis.

    PubMed

    Yokota, Yusuke; Igarashi, Yasuhiko; Okada, Masato; Naruse, Yasushi

    2015-08-01

    Quantitative estimation of the workload in the brain is an important factor for helping to predict the behavior of humans. The reaction time when performing a difficult task is longer than that when performing an easy task. Thus, the reaction time reflects the workload in the brain. In this study, we employed an N-back task in order to regulate the degree of difficulty of the tasks, and then estimated the reaction times from the brain activity. The brain activity that we used to estimate the reaction time was the auditory steady-state response (ASSR) evoked by a 40-Hz click sound. Fifteen healthy participants participated in the present study and magnetoencephalogram (MEG) responses were recorded using a 148-channel magnetometer system. The least absolute shrinkage and selection operator (LASSO), which is a type of sparse modeling, was employed to estimate the reaction times from the ASSR recorded by MEG. The LASSO showed higher estimation accuracy than the least squares method. This result indicates that LASSO overcame the over-fitting to the learning data. Furthermore, the LASSO selected channels in not only the parietal region, but also in the frontal and occipital regions. Since the ASSR is evoked by auditory stimuli, it is usually large in the parietal region. However, since LASSO also selected channels in regions outside the parietal region, this suggests that workload-related neural activity occurs in many brain regions. In the real world, it is more practical to use a wearable electroencephalography device with a limited number of channels than to use MEG. Therefore, determining which brain areas should be measured is essential. The channels selected by the sparse modeling method are informative for determining which brain areas to measure. PMID:26737821

  10. Descriptive Linear modeling of steady-state visual evoked response

    NASA Technical Reports Server (NTRS)

    Levison, W. H.; Junker, A. M.; Kenner, K.

    1986-01-01

    A study is being conducted to explore use of the steady state visual-evoke electrocortical response as an indicator of cognitive task loading. Application of linear descriptive modeling to steady state Visual Evoked Response (VER) data is summarized. Two aspects of linear modeling are reviewed: (1) unwrapping the phase-shift portion of the frequency response, and (2) parsimonious characterization of task-loading effects in terms of changes in model parameters. Model-based phase unwrapping appears to be most reliable in applications, such as manual control, where theoretical models are available. Linear descriptive modeling of the VER has not yet been shown to provide consistent and readily interpretable results.

  11. Characterizing the Relationship between Steady State and Response Using Analytical Expressions for the Steady States of Mass Action Models

    PubMed Central

    Loriaux, Paul Michael; Tesler, Glenn; Hoffmann, Alexander

    2013-01-01

    The steady states of cells affect their response to perturbation. Indeed, diagnostic markers for predicting the response to therapeutic perturbation are often based on steady state measurements. In spite of this, no method exists to systematically characterize the relationship between steady state and response. Mathematical models are established tools for studying cellular responses, but characterizing their relationship to the steady state requires that it have a parametric, or analytical, expression. For some models, this expression can be derived by the King-Altman method. However, King-Altman requires that no substrate act as an enzyme, and is therefore not applicable to most models of signal transduction. For this reason we developed py-substitution, a simple but general method for deriving analytical expressions for the steady states of mass action models. Where the King-Altman method is applicable, we show that py-substitution yields an equivalent expression, and at comparable efficiency. We use py-substitution to study the relationship between steady state and sensitivity to the anti-cancer drug candidate, dulanermin (recombinant human TRAIL). First, we use py-substitution to derive an analytical expression for the steady state of a published model of TRAIL-induced apoptosis. Next, we show that the amount of TRAIL required for cell death is sensitive to the steady state concentrations of procaspase 8 and its negative regulator, Bar, but not the other procaspase molecules. This suggests that activation of caspase 8 is a critical point in the death decision process. Finally, we show that changes in the threshold at which TRAIL results in cell death is not always equivalent to changes in the time of death, as is commonly assumed. Our work demonstrates that an analytical expression is a powerful tool for identifying steady state determinants of the cellular response to perturbation. All code is available at http://signalingsystems.ucsd.edu/models-and-code/ or

  12. Steady state visually evoked potential correlates of auditory hallucinations in schizophrenia.

    PubMed

    Line, P; Silberstein, R B; Wright, J J; Copolov, D L

    1998-11-01

    This study attempted to localize regions of brain electrical activity associated with the onset of auditory hallucinations. Changes in Steady State Visually Evoked Potential (SSVEP) topography associated with the onset of spontaneous auditory hallucinations was studied in eight schizophrenic patients. The SSVEP elicited by a spatially uniform sinusoidally varying visual flicker was recorded using a 64-channel electrode helmet. A large and significant decrease in SSVEP latency in the right temporo/parietal region occurred in the second prior to the report of auditory hallucinations. A control task with matching motor movements produced no significant decrease in SSVEP latency in the same right temporo/parietal location. This finding suggests that activity of fine temporal resolution in the neural networks in the right temporo/parietal area may be implicated in the genesis of auditory hallucination, in conformity with certain neuropsychological theories. PMID:9811555

  13. 40-Hz steady state response in Alzheimer's disease and mild cognitive impairment.

    PubMed

    van Deursen, J A; Vuurman, E F P M; van Kranen-Mastenbroek, V H J M; Verhey, F R J; Riedel, W J

    2011-01-01

    The 40-Hz steady state response (SSR) reflects early sensory processing and can be measured with electroencephalography (EEG). The current study compared the 40-Hz SSR in groups consisting of mild Alzheimer's disease patients (AD) (n=15), subjects with mild cognitive impairment (MCI) (n=20) and healthy elderly control subjects (n=20). All participants were naïve for psychoactive drugs. Auditory click trains at a frequency of 40-Hz evoked the 40-Hz SSR. To evaluate test-retest reliability (TRR), subjects underwent a similar assessment 1 week after the first. The results showed a high TRR and a significant increase of 40-Hz SSR power in the AD group compared to MCI and controls. Furthermore a moderate correlation between 40-Hz SSR power and cognitive performance as measured by ADAS-cog was shown. The results suggest that 40-Hz SSR might be an interesting candidate marker of disease progression. PMID:19237225

  14. 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

  15. Steady State Response Analysis of a Tubular Piezoelectric Print Head.

    PubMed

    Chang, Jiaqing; Liu, Yaxin; Huang, Bo

    2016-01-01

    In recent years, inkjet technology has played an important role in industrial materials printing and various sensors fabrication, but the mechanisms of the inkjet print head should be researched more elaborately. The steady state deformation analysis of a tubular piezoelectric print head, which can be classified as a plane strain problem because the radii of the tubes are considerably smaller than the lengths, is discussed in this paper. The geometric structure and the boundary conditions are all axisymmetric, so a one-dimensional mathematical model is constructed. By solving the model, the deformation field and stress field, as well as the electric potential distribution of the piezoelectric tube and glass tube, are obtained. The results show that the deformations are on the nanometer scale, the hoop stress is larger than the radial stress on the whole, and the potential is not linearly distributed along the radial direction. An experiment is designed to validate these computations. A discussion of the effect of the tubes' thicknesses on the system deformation status is provided. PMID:26771612

  16. Steady State Response Analysis of a Tubular Piezoelectric Print Head

    PubMed Central

    Chang, Jiaqing; Liu, Yaxin; Huang, Bo

    2016-01-01

    In recent years, inkjet technology has played an important role in industrial materials printing and various sensors fabrication, but the mechanisms of the inkjet print head should be researched more elaborately. The steady state deformation analysis of a tubular piezoelectric print head, which can be classified as a plane strain problem because the radii of the tubes are considerably smaller than the lengths, is discussed in this paper. The geometric structure and the boundary conditions are all axisymmetric, so a one-dimensional mathematical model is constructed. By solving the model, the deformation field and stress field, as well as the electric potential distribution of the piezoelectric tube and glass tube, are obtained. The results show that the deformations are on the nanometer scale, the hoop stress is larger than the radial stress on the whole, and the potential is not linearly distributed along the radial direction. An experiment is designed to validate these computations. A discussion of the effect of the tubes’ thicknesses on the system deformation status is provided. PMID:26771612

  17. Finite element cochlear models and their steady state response

    NASA Astrophysics Data System (ADS)

    Kagawa, Y.; Yamabuchi, T.; Watanabe, N.; Mizoguchi, T.

    1987-12-01

    Numerical cochlear models are constructed by means of a finite element approach and their frequency and spatial responses are calculated. The cochlea is modelled as a coupled fluid-membrane system, for which both two- and three-dimensional models are considered. The fluid in the scala canals is assumed to be incompressible and the basilar membrane is assumed to be a locally reactive impedance wall or a lossy elastic membrane. With the three-dimensional models, the effects are examined of the spiral configuration of the cochlea, of the presence of the lamina and the ligament that narrows the coupling area between the two fluid canals (scala vestibuli and scala tympani), and of the extended reaction of the basilar membrane which cannot be included in case of the two-dimensional models. The conclusion is that these effects on the cochlear response and the inherent mechanism governing the cochlear behaviour are found to be rather secondary.

  18. Estimation of a transient response from steady-state responses by deconvolution with built-in constraints.

    PubMed

    Lütkenhöner, Bernd

    2016-09-01

    Evidence suggests that the steady-state response (SSR) elicited by a periodic train of auditory stimuli can largely be understood as a superposition of transient responses. This study is devoted to the problem of how to estimate that transient response from measured SSRs. The proposed method differs from previous approaches in that the solution can be constrained to be consistent with physiology-based prior knowledge or educated guesses. To achieve this goal, the transient response is not represented by a time series, but by a linear combination of auxiliary functions, called components. Constraints are introduced by assigning certain properties to the components. Only few parameters are required for that purpose, because the individual components are derived from a suitably designed mother component. After adjusting the components to the problem at hand, the component amplitudes are determined by optimizing the match between predicted and measured SSRs. This requires solving a linear inverse problem. A model simulation as well as an analysis of exemplary experimental data (auditory SSRs elicited by periodically presented clicks) prove the workability of the method. Since part of the theory is quite general, it would be relatively easy to refine and extend the method. Not only could responses other than SSRs be dealt with, it could also be realized that certain key parameters of the transient response, such as amplitude and delay, depend on stimulus repetition rate. PMID:27234643

  19. Development of an annoyance model based upon elementary auditory sensations for steady-state aircraft interior noise containing tonal components

    NASA Technical Reports Server (NTRS)

    Angerer, James R.; Mccurdy, David A.; Erickson, Richard A.

    1991-01-01

    The purpose of this investigation was to develop a noise annoyance model, superior to those already in use, for evaluating passenger response to sounds containing tonal components which may be heard within current and future commercial aircraft. The sound spectra investigated ranged from those being experienced by passengers on board turbofan powered aircraft now in service to those cabin noise spectra passengers may experience within advanced propeller-driven aircraft of the future. A total of 240 sounds were tested in this experiment. Sixty-six of these 240 sounds were steady state, while the other 174 varied temporally due to tonal beating. Here, the entire experiment is described, but the analysis is limited to those responses elicited by the 66 steady-state sounds.

  20. Proteome analysis of the Escherichia coli heat shock response under steady-state conditions

    PubMed Central

    Lüders, Svenja; Fallet, Claas; Franco-Lara, Ezequiel

    2009-01-01

    In this study a proteomic approach was used to investigate the steady-state response of Escherichia coli to temperature up-shifts in a cascade of two continuously operated bioreactors. The first reactor served as cell source with optimal settings for microbial growth, while in the second chemostat the cells were exposed to elevated temperatures. By using this reactor configuration, which has not been reported to be used for the study of bacterial stress responses so far, it is possible to study temperature stress under well-defined, steady-state conditions. Specifically the effect on the cellular adaption to temperature stress using two-dimensional gel electrophoresis was examined and compared at the cultivation temperatures of 37°C and 47.5°C. As expected, the steady-state study with the double bioreactor configuration delivered a different protein spectrum compared to that obtained with standard batch experiments in shaking flasks and bioreactors. Setting a high cut-out spot-to-spot size ratio of 5, proteins involved in defence against oxygen stress, functional cell envelope proteins, chaperones and proteins involved in protein biosynthesis, the energy metabolism and the amino acid biosynthesis were found to be differently expressed at high cultivation temperatures. The results demonstrate the complexity of the stress response in a steady-state culture not reported elsewhere to date. PMID:19772559

  1. Steady-state BOLD Response to Higher-order Cognition Modulates Low-Frequency Neural Oscillations.

    PubMed

    Wang, Yi-Feng; Dai, Gang-Shu; Liu, Feng; Long, Zhi-Liang; Yan, Jin H; Chen, Hua-Fu

    2015-12-01

    Steady-state responses (SSRs) reflect the synchronous neural oscillations evoked by noninvasive and consistently repeated stimuli at the fundamental or harmonic frequencies. The steady-state evoked potentials (SSEPs; the representative form of the SSRs) have been widely used in the cognitive and clinical neurosciences and brain-computer interface research. However, the steady-state evoked potentials have limitations in examining high-frequency neural oscillations and basic cognition. In addition, synchronous neural oscillations in the low frequency range (<1 Hz) and in higher-order cognition have received a little attention. Therefore, we examined the SSRs in the low frequency range using a new index, the steady-state BOLD responses (SSBRs) evoked by semantic stimuli. Our results revealed that the significant SSBRs were induced at the fundamental frequency of stimuli and the first harmonic in task-related regions, suggesting the enhanced variability of neural oscillations entrained by exogenous stimuli. The SSBRs were independent of neurovascular coupling and characterized by sensorimotor bias, an indication of regional-dependent neuroplasticity. Furthermore, the amplitude of SSBRs may predict behavioral performance and show the psychophysiological relevance. Our findings provide valuable insights into the understanding of the SSRs evoked by higher-order cognition and how the SSRs modulate low-frequency neural oscillations. PMID:26284992

  2. VIBRA: An interactive computer program for steady-state vibration response analysis of linear damped structures

    NASA Technical Reports Server (NTRS)

    Bowman, L. M.

    1984-01-01

    An interactive steady state frequency response computer program with graphics is documented. Single or multiple forces may be applied to the structure using a modal superposition approach to calculate response. The method can be reapplied to linear, proportionally damped structures in which the damping may be viscous or structural. The theoretical approach and program organization are described. Example problems, user instructions, and a sample interactive session are given to demonstate the program's capability in solving a variety of problems.

  3. MEG-measured auditory steady-state oscillations show high test-retest reliability: A sensor and source-space analysis.

    PubMed

    Tan, H-R M; Gross, J; Uhlhaas, P J

    2015-11-15

    Stability of oscillatory signatures across magnetoencephalography (MEG) measurements is an important prerequisite for basic and clinical research that has been insufficiently addressed. Here, we evaluated the test-retest reliability of auditory steady-state responses (ASSRs) over two MEG sessions. The study required participants (N=13) to detect the rare occurrence of pure tones interspersed within a stream of 5 Hz or 40 Hz amplitude-modulated (AM) tones. Intraclass correlations (ICC; Shrout and Fleiss, 1979) were derived to assess stability of spectral power changes and the inter-trial phase coherence (ITPC) of task-elicited neural responses. ASSRs source activity was estimated using eLORETA beamforming from bilateral auditory cortex. ASSRs to 40 Hz AM stimuli evoked stronger power modulation and phase-locking than 5 Hz stimulation. Overall, spectral power and ITPC values at both sensor- and source-level showed robust ICC values. Notably, ITPC measures yielded higher ICCs (~0.86-0.96) between sessions compared to the assessment of spectral power change (~0.61-0.82). Our data indicate that spectral modulations and phase consistency of ASSRs in MEG data are highly reproducible, providing support for MEG-measured oscillatory parameters in basic and clinical research. PMID:26216274

  4. Metabolic responses from rest to steady state determine contractile function in ischemic skeletal muscle.

    PubMed

    Timmons, J A; Poucher, S M; Constantin-Teodosiu, D; Macdonald, I A; Greenhaff, P L

    1997-08-01

    Skeletal muscle contraction during ischemia, such as that experienced by peripheral vascular disease patients, is characterized by rapid fatigue. Using a canine gracilis model, we tested the hypothesis that a critical factor determining force production during ischemia is the metabolic response during the transition from rest to steady state. Dichloroacetate (DCA) administration before gracilis muscle contraction increased pyruvate dehydrogenase complex activation and resulted in acetylation of 80% of the free carnitine pool to acetylcarnitine. After 1 min of contraction, phosphocreatine (PCr) degradation in the DCA group was approximately 50% lower than in the control group (P < 0.05) during conditions of identical force production. After 6 min of contraction, steady-state force production was approximately 30% higher in the DCA group (P < 0.05), and muscle ATP, PCr, and glycogen degradation and lactate accumulation were lower (P < 0.05 in all cases). It appears, therefore, that an important determinant of contractile function during ischemia is the mechanisms by which ATP regeneration occurs during the period of rest to steady-state transition. PMID:9277374

  5. The VERRUN and VERNAL software systems for steady-state visual evoked response experimentation

    NASA Technical Reports Server (NTRS)

    Levison, W. H.; Zacharias, G. L.

    1984-01-01

    Two digital computer programs were developed for use in experiments involving steady-state visual evoked response (VER): VERRUN, whose primary functions are to generate a sum-of-sines (SOS) stimulus and to digitize and store electro-cortical response; and VERNAL, which provides both time- and frequency-domain metrics of the evoked response. These programs were coded in FORTRAN for operation on the PDP-11/34, using the RSX-11 Operating System, and the PDP-11/23, using the RT-11 Operating System. Users' and programmers' guides to these programs are provided, and guidelines for model analysis of VER data are suggested.

  6. Simulation on the Comparison of Steady-State Responses Synthesized by Transient Templates Based on Superposition Hypothesis

    PubMed Central

    Tan, Xiao-dan; Yu, Xue-fei; Lin, Lin; Wang, Tao

    2015-01-01

    The generation of auditory-evoked steady-state responses (SSRs) is associated with the linear superposition of transient auditory-evoked potentials (AEPs) that cannot be directly observed. A straightforward way to justify the superposition hypothesis is the use of synthesized SSRs by a transient AEP under a predefined condition based on the forward process of this hypothesis. However, little is known about the inverse relation between the transient AEP and its synthetic SSR, which makes the interpretation of the latter less convincible because it may not necessarily underlie the true solution. In this study, we chose two pairs of AEPs from the conventional and deconvolution paradigms, which represent the homo-AEPs from a homogenous group and the hetero-AEPs from two heterogeneous groups. Both pairs of AEPs were used as templates to synthesize SSRs at rates of 20–120 Hz. The peak-peak amplitudes and the differences between the paired waves were measured. Although amplitude enhancement occurred at ~40 Hz, comparisons between the available waves demonstrated that the relative differences of the synthetic SSRs could be dramatically larger at other rates. Moreover, two virtually identical SSRs may come from clearly different AEPs. These results suggested inconsistent relationships between the AEPs and their corresponding SSRs over the tested rates. PMID:26600868

  7. Steady-state responses of a belt-drive dynamical system under dual excitations

    NASA Astrophysics Data System (ADS)

    Ding, Hu

    2016-02-01

    The stable steady-state periodic responses of a belt-drive system with a one-way clutch are studied. For the first time, the dynamical system is investigated under dual excitations. The system is simultaneously excited by the firing pulsations of the engine and the harmonic motion of the foundation. Nonlinear discrete-continuous equations are derived for coupling the transverse vibration of the belt spans and the rotations of the driving and driven pulleys and the accessory pulley. The nonlinear dynamics is studied under equal and multiple relations between the frequency of the firing pulsations and the frequency of the foundation motion. Furthermore, translating belt spans are modeled as axially moving strings. A set of nonlinear piecewise ordinary differential equations is achieved by using the Galerkin truncation. Under various relations between the excitation frequencies, the time histories of the dynamical system are numerically simulated based on the time discretization method. Furthermore, the stable steady-state periodic response curves are calculated based on the frequency sweep. Moreover, the convergence of the Galerkin truncation is examined. Numerical results demonstrate that the one-way clutch reduces the resonance amplitude of the rotations of the driven pulley and the accessory pulley. On the other hand, numerical examples prove that the resonance areas of the belt spans are decreased by eliminating the torque-transmitting in the opposite direction. With the increasing amplitude of the foundation excitation, the damping effect of the one-way clutch will be reduced. Furthermore, as the amplitude of the firing pulsations of the engine increases, the jumping phenomena in steady-state response curves of the belt-drive system with or without a one-way clutch both occur.

  8. Steady-State and Frequency Response of a Thin-Film Heat Flux Gauge

    NASA Technical Reports Server (NTRS)

    Fralick, Gustave C.; Bhatt, Hemanshu D.; Cho, Chistopher S.

    1997-01-01

    A new and simpler design of thin-film heat flux gauge has been developed for use In high-heat-flux environments. Heat flux gauges of the same design were fabricated on three different substrates and tested. The heat flux gauge comprises a thermopile and a thermocouple junction, which measures the surface temperature. The thermopile has 40 pairs of S-type thermocouples and is covered by two thermal resistance layers. Calibration and testing of these gauges were first carried out in an arc-lamp calibration facility. Sensitivity of the gauge was discussed in terms of the relative conductivity and surface temperature. The heat flux calculated from the gauge output was In good agreement with the precalibrated standard sensor. The steady-state and the transient response characteristics of the heat flux gauge were also investigated using a carbon dioxide pulse laser as a heat source. The dynamic frequency response was evaluated in terms of the nondimensional amplitude ratio with respect to the frequency spectrum of a chopped laser bcam. The frequency response of the gauge was determined to be about 3 kHz. The temperature profiles in the thin-film heat flux gauge were obtained numerically in steady-state conditions using FLUENT and compared with the experimental results.

  9. Radiofrequency quadrupolar NMR stark spectroscopy: steady state response calibration and tensorial mapping.

    PubMed

    Tarasek, Matthew R; Kempf, James G

    2010-10-01

    Radiofrequency electric (E) fields oscillating at twice the usual NMR frequency (2ω(0)) can induce double-quantum transitions in quadrupolar nuclei, an NMR Stark effect. Characterization of such is of interest to aid understanding of electrostatic effects in NMR spectra. Calibration of Stark responses to an applied electric field may also be used to assess native fields within molecules and materials. We present high-field (14.1 T), room-temperature NMR experiments to calibrate the 2ω(0) Stark response in crystalline GaAs. This system presents an important test of current techniques and conditions, as historical studies at low field (500-900 mT) and low temperature (77 K) provide a basis for comparison. Our measurements of steady state response reveal the quadrupolar Stark tuning rate for (69)Ga in this material. The value, β(Q) = (11.5 ± 0.1) × 10(12) m(-1), is 3.6 times larger than the most-reliable prior result. In the process, we also uncovered a previously unobserved double-quantum steady state coherence. It appears as a completely separable dispersive signal component in quadrature-detected presaturation spectra versus offset from 2ω(0). The new component may eventually afford an independent route to calibrating β(Q). Finally, we demonstrated exceptional agreement with theory of the orientation-dependent Stark response for rotation of the sample relative to B(0) over a range of 90° and for E-field amplitudes from 30-180 V/cm. PMID:20839890

  10. Inverse solution technique of steady-state responses for local nonlinear structures

    NASA Astrophysics Data System (ADS)

    Wang, Xing; Guan, Xin; Zheng, Gangtie

    2016-03-01

    An inverse solution technique with the ability of obtaining complete steady-state primary harmonic responses of local nonlinear structures in the frequency domain is proposed in the present paper. In this method, the nonlinear dynamic equations of motion is first condensed from many to only one algebraic amplitude-frequency equation of relative motion. Then this equation is transformed into a polynomial form, and with its frequency as the unknown variable, the polynomial equation is solved by tracing all the solutions of frequency with the increase of amplitude. With this solution technique, some complicated dynamic behaviors such as sharp tuning, anomalous jumps, breaks in responses and detached resonance curves could be obtained. The proposed method is demonstrated and validated through a finite element beam under force excitations and a lumped parameter model with a local nonlinear element under base excitations. The phenomenon of detached resonance curves in the frequency response and its coupling effects with multiple linear modes in the latter example are observed.

  11. Precise mapping of the somatotopic hand area using neuromagnetic steady-state responses.

    PubMed

    Jamali, Shahab; Ross, Bernhard

    2012-05-21

    The body surface is represented in somatotopically organized maps in the primary somatosensory cortex. Estimating the size of the hand area with neuromagnetic source analysis has been used as a metric for monitoring neuroplastic changes related to training, learning, and brain injury. Commonly, results were significant as group statistics only because source localization accuracy was limited by factors such as residual noise and head motion. In this study we aimed to develop a robust method for obtaining the somatotopic map of the hand area in individuals using the bootstrap framework. Furthermore, a comprehensive analysis of the different factors affecting the accuracy of the obtained maps was provided. We applied vibrotactile touch stimuli to the tip of the index finger or the ring finger of the right hand and recorded the 22-Hz steady-state response using MEG. Single equivalent dipole sources were localized in contralateral left somatosensory cortex. Bootstrap resampling revealed the confidence intervals for the source coordinates using a single block of 5 min MEG recording. Residual noise in the averaged evoked response predominantly affected source localization, and the related confidence interval was reciprocally related to the signal-to-noise ratio. Apparently, head movements within a block of MEG recording contributed less to the variability of source localization in cooperative volunteers. The results of the current study indicate that significant separations of index finger and ring finger representations along the somatotopic map can be revealed in an individual using bootstrap framework. PMID:22507747

  12. Steady-State Contrast Response Functions Provide a Sensitive and Objective Index of Amblyopic Deficits

    PubMed Central

    Baker, Daniel H.; Simard, Mathieu; Saint-Amour, Dave; Hess, Robert F.

    2015-01-01

    Purpose. Visual deficits in amblyopia are neural in origin, yet are difficult to characterize with functional magnetic resonance imagery (fMRI). Our aim was to develop an objective electroencephalography (EEG) paradigm that can be used to provide a clinically useful index of amblyopic deficits. Methods. We used steady-state visual evoked potentials (SSVEPs) to measure full contrast response functions in both amblyopic (n = 10, strabismic or mixed amblyopia, mean age: 44 years) and control (n = 5, mean age: 31 years) observers, both with and without a dichoptic mask. Results. At the highest target contrast, the ratio of amplitudes across the weaker and stronger eyes was highly correlated (r = 0.76) with the acuity ratio between the eyes. We also found that the contrast response function in the amblyopic eye had both a greatly reduced amplitude and a shallower slope, but that surprisingly dichoptic masking was weaker than in controls. The results were compared with the predictions of a computational model of amblyopia and suggest a modification to the model whereby excitatory (but not suppressive) signals are attenuated in the amblyopic eye. Conclusions. We suggest that SSVEPs offer a sensitive and objective measure of the ocular imbalance in amblyopia and could be used to assess the efficacy of amblyopia therapies currently under development. PMID:25634977

  13. A multi-signature brain-computer interface: use of transient and steady-state responses

    NASA Astrophysics Data System (ADS)

    Severens, Marianne; Farquhar, Jason; Duysens, Jacques; Desain, Peter

    2013-04-01

    Objective. The aim of this paper was to increase the information transfer in brain-computer interfaces (BCI). Therefore, a multi-signature BCI was developed and investigated. Stimuli were designed to simultaneously evoke transient somatosensory event-related potentials (ERPs) and steady-state somatosensory potentials (SSSEPs) and the ERPs and SSSEPs in isolation. Approach. Twelve subjects participated in two sessions. In the first session, the single and combined stimulation conditions were compared on these somatosensory responses and on the classification performance. In the second session the on-line performance with the combined stimulation was evaluated while subjects received feedback. Furthermore, in both sessions, the performance based on ERP and SSSEP features was compared. Main results. No difference was found in the ERPs and SSSEPs between stimulation conditions. The combination of ERP and SSSEP features did not perform better than with ERP features only. In both sessions, the classification performances based on ERP and combined features were higher than the classification based on SSSEP features. Significance. Although the multi-signature BCI did not increase performance, it also did not negatively impact it. Therefore, such stimuli could be used and the best performing feature set could then be chosen individually.

  14. The influence of visual perspective on the somatosensory steady-state response during pain observation

    PubMed Central

    Canizales, Dora L.; Voisin, Julien I. A.; Michon, Pierre-Emmanuel; Roy, Marc-André; Jackson, Philip L.

    2013-01-01

    The observation and evaluation of other’s pain activate part of the neuronal network involved in the actual experience of pain, including those regions subserving the sensori-discriminative dimension of pain. This was largely interpreted as evidence showing that part of the painful experience can be shared vicariously. Here, we investigated the effect of the visual perspective from which other people’s pain is seen on the cortical response to continuous 25 Hz non-painful somatosensory stimulation (somatosensory steady-state response: SSSR). Based on the shared representation framework, we expected first-person visual perspective (1PP) to yield more changes in cortical activity than third-person visual perspective (3PP) during pain observation. Twenty healthy adults were instructed to rate a series of pseudo-dynamic pictures depicting hands in either painful or non-painful scenarios, presented either in 1PP (0–45° angle) or 3PP (180° angle), while changes in brain activity was measured with a 128-electode EEG system. The ratings demonstrated that the same scenarios were rated on average as more painful when observed from the 1PP than from the 3PP. As expected from previous works, the SSSR response was decreased after stimulus onset over the left caudal part of the parieto-central cortex, contralateral to the stimulation side. Moreover, the difference between the SSSR was of greater amplitude when the painful situations were presented from the 1PP compared to the 3PP. Together, these results suggest that a visuospatial congruence between the viewer and the observed scenarios is associated with both a higher subjective evaluation of pain and an increased modulation in the somatosensory representation of observed pain. These findings are discussed with regards to the potential role of visual perspective in pain communication and empathy. PMID:24367323

  15. The steady-state response of the cerebral cortex to the beat of music reflects both the comprehension of music and attention

    PubMed Central

    Meltzer, Benjamin; Reichenbach, Chagit S.; Braiman, Chananel; Schiff, Nicholas D.; Hudspeth, A. J.; Reichenbach, Tobias

    2015-01-01

    The brain’s analyses of speech and music share a range of neural resources and mechanisms. Music displays a temporal structure of complexity similar to that of speech, unfolds over comparable timescales, and elicits cognitive demands in tasks involving comprehension and attention. During speech processing, synchronized neural activity of the cerebral cortex in the delta and theta frequency bands tracks the envelope of a speech signal, and this neural activity is modulated by high-level cortical functions such as speech comprehension and attention. It remains unclear, however, whether the cortex also responds to the natural rhythmic structure of music and how the response, if present, is influenced by higher cognitive processes. Here we employ electroencephalography to show that the cortex responds to the beat of music and that this steady-state response reflects musical comprehension and attention. We show that the cortical response to the beat is weaker when subjects listen to a familiar tune than when they listen to an unfamiliar, non-sensical musical piece. Furthermore, we show that in a task of intermodal attention there is a larger neural response at the beat frequency when subjects attend to a musical stimulus than when they ignore the auditory signal and instead focus on a visual one. Our findings may be applied in clinical assessments of auditory processing and music cognition as well as in the construction of auditory brain-machine interfaces. PMID:26300760

  16. The steady-state response of the cerebral cortex to the beat of music reflects both the comprehension of music and attention.

    PubMed

    Meltzer, Benjamin; Reichenbach, Chagit S; Braiman, Chananel; Schiff, Nicholas D; Hudspeth, A J; Reichenbach, Tobias

    2015-01-01

    The brain's analyses of speech and music share a range of neural resources and mechanisms. Music displays a temporal structure of complexity similar to that of speech, unfolds over comparable timescales, and elicits cognitive demands in tasks involving comprehension and attention. During speech processing, synchronized neural activity of the cerebral cortex in the delta and theta frequency bands tracks the envelope of a speech signal, and this neural activity is modulated by high-level cortical functions such as speech comprehension and attention. It remains unclear, however, whether the cortex also responds to the natural rhythmic structure of music and how the response, if present, is influenced by higher cognitive processes. Here we employ electroencephalography to show that the cortex responds to the beat of music and that this steady-state response reflects musical comprehension and attention. We show that the cortical response to the beat is weaker when subjects listen to a familiar tune than when they listen to an unfamiliar, non-sensical musical piece. Furthermore, we show that in a task of intermodal attention there is a larger neural response at the beat frequency when subjects attend to a musical stimulus than when they ignore the auditory signal and instead focus on a visual one. Our findings may be applied in clinical assessments of auditory processing and music cognition as well as in the construction of auditory brain-machine interfaces. PMID:26300760

  17. Inhibition of steady-state smooth pursuit and catch-up saccades by abrupt visual and auditory onsets.

    PubMed

    Kerzel, Dirk; Born, Sabine; Souto, David

    2010-11-01

    It is known that visual transients prolong saccadic latency and reduce saccadic frequency. The latter effect was attributed to subcortical structures because it occurred only 60-70 ms after stimulus onset. We examined the effects of large task-irrelevant transients on steady-state pursuit and the generation of catch-up saccades. Two screen-wide stripes of equal contrast (4, 20, or 100%) were briefly flashed at equal eccentricities (3, 6, or 12°) from the pursuit target. About 100 ms after flash onset, we observed that pursuit gain dropped by 6-12% and catch-up saccades were entirely suppressed. The relatively long latency of the inhibition suggests that it results from cortical mechanisms that may act by promoting fixation or the deployment of attention over the visual field. In addition, we show that a loud irrelevant sound is able to generate the same inhibition of saccades as visual transients, whereas it only induces a weak modulation of pursuit gain, indicating a privileged access of acoustic information to the saccadic system. Finally, irrelevant changes in motion direction orthogonal to pursuit had a smaller and later inhibitory effect. PMID:20844111

  18. Human stance control beyond steady state response and inverted pendulum simplification.

    PubMed

    Schweigart, G; Mergner, T

    2008-03-01

    Systems theory analyses have suggested that human upright stance can be modelled in terms of continuous multi-sensory feedback control. So far, these analyses have considered mainly steady-state responses to periodic stimuli and relied on a simplifying model of the body's mechanics in the form of an inverted pendulum. Therefore, they may have ignored relevant aspects of the postural behaviour. To prove a more general validity of a stance control model that we previously derived from such analyses, we now presented subjects with static-dynamic stimulus combinations and assessed response transients, anterior-posterior (a-p) response asymmetries, and possible deviations from the 'inverted pendulum' simplification (by measuring hip and knee bending). We presented normal subjects (Ns) and vestibular loss patients (Ps) with a-p support surface tilt on a motion platform under the instruction to maintain, with eyes closed, the body upright in space. In addition, subjects were to indicate perceived platform tilt with the help of pointers. We combined a fixed-amplitude sinusoidal tilt (0.1 Hz) with static tilts that were varied in amplitude and direction. We recorded upper body (shoulder) and lower body (hip) excursions in space and centre of pressure (COP) shift, and calculated the centre of mass (COM) angular excursion. We found that: (1) Immediately prior to stimulus onset (which was highly predictable), subjects showed a small anticipatory forward lean. (2) The subsequent transient response consisted of two parts. First, the body was moved along with the platform tilt and then, in the second part, the body excursion was braked by starting tilt compensation. Upon increasing tilt amplitude, the braking point showed a pronounced saturation with for-aft asymmetry. (3) During the following prolonged tilt, the tonic body excursions saturated with increasing static tilt amplitude. This saturation also showed a for-aft asymmetry (backwards saturation more pronounced). In

  19. Transient and Steady-State Kinematic Response to Erosional Forcing in an Orogenic Wedge: Sandbox Perspective

    NASA Astrophysics Data System (ADS)

    Cruz, L.; Teyssier, C.; Annia, F.; Take, A.

    2005-12-01

    The evolution of orogens is highly affected by surface processes that control mass distribution. Transportation and redistribution of mass at the Earth's surface modifies the gravitational load and alters the stress field and kinematics within orogens. We explore the role of asymmetric erosion, indenter dip angle, and flux steady/non-steady state in determining the patterns of deformation and exhumation in doubly-sided orogenic wedges. In our analogue model, shortening of the orogen is driven by rigid indenters, represented by Plexiglas wedged blocks (35 and 70 degrees) that deform a non-cohesive dry Coulomb material (walnut shells) representing crustal material. Three end-member erosional scenarios are considered. In the first case, erosion is not applied, and thus the doubly-sided orogenic wedge evolves without restraints (non-steady state). In the second case, erosion is concentrated solely on the indenters side of the orogen (retrowedge), and in the third case, erosion is focused on the flank opposite to the indenter side (prowedge). In the last two cases, steady-state conditions were present in the middle stages of shortening. Strain and exhumation were calculated using displacement fields from 2D particle image velocimetry (PIV analysis). In the three cases, the model deforms as a combination of lateral compaction and localization of strain in shear bands. In the early stages of deformation, a "pop-up" structure develops, bounded by a fore-shear on the front and a back-shear toward the indenter. As deformation continues, a new fore-shear develops, and the previous one remains inactive and is passively pushed up the wedge. In the case of no erosion, the old fore-shears rotate slightly toward the indenter, and the shear bands evolve to steeply dipping structures. In the case of retrowedge erosion, the old fore-shears back rotate toward the indenter, and the shear bands evolve to shallowly dipping structures. In the case of prowedge erosion, old fore

  20. Steady-state response of a charcoal bed to radon in flowing air with water vapor

    SciTech Connect

    Blue, T.E.; Jarzemba, M.S.; Fentiman, A.W.

    1995-06-01

    Previously we have developed a mathematical model of radon adsorption in active air with water vapor on small U.S. Environmental Protection Agency charcoal canisters that are used for environmental measurements of radon. The purpose of this paper is to extend this mathematical model to describe the adsorption of radon by large charcoal beds with radon-laden air flowing through them. The resulting model equations are solved analytically to predict the steady-state adsorption of radon by such beds. 14 refs., 3 figs.

  1. Transient and steady state creep response of ice I and magnesium sulfate hydrate eutectic aggregates

    NASA Astrophysics Data System (ADS)

    McCarthy, Christine; Cooper, Reid F.; Goldsby, David L.; Durham, William B.; Kirby, Stephen H.

    2011-04-01

    Using uniaxial compression creep experiments, we characterized the transient and steady state deformation behaviors of eutectic aggregates of system ice I and MgSO4 • 11H2O (MS11; meridianiite), which has significance because of its likely presence on moons of the outer solar system. Synthetic samples of eutectic liquid bulk composition, which produce eutectic colonies containing 0.35-0.50 volume fraction MS11, were tested as functions of colony size and lamellar spacing, temperature (230-250 K), and confining pressure (0.1 and 50 MPa) to strains ≤ 0.2. Up to a differential stress of 6 MPa, the ice I-MS11 aggregates display an order of magnitude higher effective viscosity and higher stress sensitivity than do aggregates of pure polycrystalline ice at the same conditions. The creep data and associated microstructural observations demonstrate, however, that the aggregates are additionally more brittle than pure ice, approaching rate-independent plasticity that includes rupture of the hydrate phase at 6-8 MPa, depending on the scale of the microstructure. Microstructures of deformed samples reveal forms of semibrittle flow in which the hydrate phase fractures while the ice phase deforms plastically. Semibrittle flow in the icy shell of a planetary body would truncate the lithospheric strength envelope and thereby decrease the depth to the brittle-ductile transition by 55% and reduce the failure limit for compressional surface features from 10 to ˜6 MPa. A constitutive equation that includes eutectic colony boundary sliding and intracolony flow is used to describe the steady state rheology of the eutectic aggregates.

  2. Transient and steady state creep response of ice I and magnesium sulfate hydrate eutectic aggregates

    USGS Publications Warehouse

    McCarthy, C.; Cooper, R.F.; Goldsby, D.L.; Durham, W.B.; Kirby, S.H.

    2011-01-01

    Using uniaxial compression creep experiments, we characterized the transient and steady state deformation behaviors of eutectic aggregates of system ice I and MgSO4 11H2O (MS11; meridianiite), which has significance because of its likely presence on moons of the outer solar system. Synthetic samples of eutectic liquid bulk composition, which produce eutectic colonies containing 0.35-0.50 volume fraction MS11, were tested as functions of colony size and lamellar spacing, temperature (230-250 K), and confining pressure (0.1 and 50 MPa) to strains ???0.2. Up to a differential stress of 6 MPa, the ice I-MS11 aggregates display an order of magnitude higher effective viscosity and higher stress sensitivity than do aggregates of pure polycrystalline ice at the same conditions. The creep data and associated microstructural observations demonstrate, however, that the aggregates are additionally more brittle than pure ice, approaching rate-independent plasticity that includes rupture of the hydrate phase at 6-8 MPa, depending on the scale of the microstructure. Microstructures of deformed samples reveal forms of semibrittle flow in which the hydrate phase fractures while the ice phase deforms plastically. Semibrittle flow in the icy shell of a planetary body would truncate the lithospheric strength envelope and thereby decrease the depth to the brittle-ductile transition by 55% and reduce the failure limit for compressional surface features from 10 to ???6 MPa. A constitutive equation that includes eutectic colony boundary sliding and intracolony flow is used to describe the steady state rheology of the eutectic aggregates. Copyright ?? 2011 by the American Geophysical Union.

  3. Auditory steady-state evoked potentials vs. compound action potentials for the measurement of suppression tuning curves in the sedated dog puppy.

    PubMed

    Markessis, Emily; Poncelet, Luc; Colin, Cécile; Hoonhorst, Ingrid; Collet, Grégory; Deltenre, Paul; Moore, Brian C J

    2010-06-01

    Auditory steady-state evoked potential (ASSEP) tuning curves were compared to compound action potential (CAP) tuning curves, both measured at 2 Hz, using sedated beagle puppies. The effect of two types of masker (narrowband noise and sinusoidal) on the tuning curve parameters was assessed. Whatever the masker type, CAP tuning curve parameters were qualitatively and quantitatively similar to the ASSEP ones, with a similar inter-subject variability, but with a greater incidence of upward tip displacement. Whatever the procedure, sinusoidal maskers produced sharper tuning curves than narrow-band maskers. Although these differences are not likely to have significant implications for clinical work, from a fundamental point of view, their origin requires further investigations. The same amount of time was needed to record a CAP and an ASSEP 13-point tuning curve. The data further validate the ASSEP technique, which has the advantages of having a smaller tendency to produce upward tip shifts than the CAP technique. Moreover, being non invasive, ASSEP tuning curves can be easily repeated over time in the same subject for clinical and research purposes. PMID:20482293

  4. On the nonlinear steady-state response of rigid rotors supported by air foil bearings-Theory and experiments

    NASA Astrophysics Data System (ADS)

    Larsen, Jon S.; Santos, Ilmar F.

    2015-06-01

    The demand for oil-free turbo compressors is increasing. Current trends are divided between active magnetic bearings and air foil bearings (AFB), the latter being important due to mechanical simplicity. AFB supported rotors are sensitive to unbalance due to low damping and nonlinear characteristics, hence accurate prediction of their response is important. This paper gives theoretical and experimental contributions by implementing and validating a new method to simulate the nonlinear steady-state response of a rotor supported by three pads segmented AFBs. The fluid film pressures, foil deflections and rotor movements are simultaneously solved, considering foil stiffness and damping coefficients estimated using a structural model, previously described and validated against experiments.

  5. Auditory evoked responses to rhythmic sound pulses in dolphins.

    PubMed

    Popov, V V; Supin, A Y

    1998-10-01

    The ability of auditory evoked potentials to follow sound pulse (click or pip) rate was studied in bottlenosed dolphins. Sound pulses were presented in 20-ms rhythmic trains separated by 80-ms pauses. Rhythmic click or pip trains evoked a quasi-sustained response consisting of a sequence of auditory brainstem responses. This was designated as the rate-following response. Rate following response peak-to-peak amplitude dependence on sound pulse rate was almost flat up to 200 s-1, then displayed a few peaks and valleys superimposed on a low-pass filtering function with a cut-off frequency of 1700 s-1 at a 0.1-amplitude level. Peaks and valleys of the function corresponded to the pattern of the single auditory brain stem response spectrum; the low-pass cut-off frequency was below the auditory brain stem response spectrum bandwidth. Rate-following response frequency composition (magnitudes of the fundamental and harmonics) corresponded to the auditory brain stem response frequency spectrum except for lower fundamental magnitudes at frequencies above 1700 Hz. These regularities were similar for both click and pip trains. The rate-following response to steady-state rhythmic stimulation was similar to the rate-following response evoked by short trains except for a slight amplitude decrease with the rate increase above 10 s-1. The latter effect is attributed to a long-term rate-dependent adaptation in conditions of the steady-state pulse stimulation. PMID:9809455

  6. A new method for predicting response in complex linear systems. II. [under random or deterministic steady state excitation

    NASA Technical Reports Server (NTRS)

    Bogdanoff, J. L.; Kayser, K.; Krieger, W.

    1977-01-01

    The paper describes convergence and response studies in the low frequency range of complex systems, particularly with low values of damping of different distributions, and reports on the modification of the relaxation procedure required under these conditions. A new method is presented for response estimation in complex lumped parameter linear systems under random or deterministic steady state excitation. The essence of the method is the use of relaxation procedures with a suitable error function to find the estimated response; natural frequencies and normal modes are not computed. For a 45 degree of freedom system, and two relaxation procedures, convergence studies and frequency response estimates were performed. The low frequency studies are considered in the framework of earlier studies (Kayser and Bogdanoff, 1975) involving the mid to high frequency range.

  7. Cerebrovascular responsiveness to steady-state changes in end-tidal CO2 during passive heat stress

    PubMed Central

    Low, David A.; Wingo, Jonathan E.; Keller, David M.; Davis, Scott L.; Zhang, Rong; Crandall, Craig G.

    2009-01-01

    This study tested the hypothesis that passive heat stress alters cerebrovascular responsiveness to steady-state changes in end-tidal CO2 (PetCO2). Nine healthy subjects (4 men and 5 women), each dressed in a water-perfused suit, underwent normoxic hypocapnic hyperventilation (decrease PetCO2 ~20 Torr) and normoxic hypercapnic (increase in PetCO2 ~9 Torr) challenges under normothermic and passive heat stress conditions. The slope of the relationship between calculated cerebrovascular conductance (CBVC; middle cerebral artery blood velocity/mean arterial blood pressure) and PetCO2 was used to evaluate cerebrovascular CO2 responsiveness. Passive heat stress increased core temperature (1.1 ± 0.2°C, P < 0.001) and reduced middle cerebral artery blood velocity by 8 ± 8 cm/s (P = 0.01), reduced CBVC by 0.09 ± 0.09 CBVC units (P = 0.02), and decreased PetCO2 by 3 ± 4 Torr (P = 0.07), while mean arterial blood pressure was well maintained (P = 0.36). The slope of the CBVC-PetCO2 relationship to the hypocapnic challenge was not different between normothermia and heat stress conditions (0.009 ± 0.006 vs. 0.009 ± 0.004 CBVC units/Torr, P = 0.63). Similarly, in response to the hypercapnic challenge, the slope of the CBVC-PetCO2 relationship was not different between normothermia and heat stress conditions (0.028 ± 0.020 vs. 0.023 ± 0.008 CBVC units/Torr, P = 0.31). These results indicate that cerebrovascular CO2 responsiveness, to the prescribed steady-state changes in PetCO2, is unchanged during passive heat stress. PMID:18218916

  8. Steady state respiratory responses to tasks used in Federal testing of self-contained breathing apparatus.

    PubMed

    Kamon, E; Bernard, T; Stein, R

    1975-12-01

    A portion of Title 30, Part II, CFR calls for a Man Test, which is a series of regimens performed with a breathing apparatus. The respiratory responses to the tasks in the Man Test were established on coal miners and students. Based on these responses, the minimal metabolic requirements were derived for the use of breathing apparatuses with a service life of 30 minutes or more. PMID:1211359

  9. Steady-state unbalance response of a three-disk flexible rotor on flexible, damped supports

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1977-01-01

    Experimental data are presented for the unbalance response of a flexible, ball bearing supported rotor to speeds above the third lateral bending critical. Values of squeeze film damping coefficients obtained from measured data are compared to theoretical values obtained from short bearing approximation over a frequency range from 5000 to 31 000 cycles/min. Experimental response for an undamped rotor is compared to that of one having oil squeeze film dampers at the bearings. Unbalance applied varied from 0.62 to 15.1 gm-cm.

  10. Steady-state unbalance response of a three-disk flexible rotor on flexible, damped supports

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1977-01-01

    Experimental data are presented for the unbalance response of a flexible, ball bearing supported rotor to speeds above the third lateral bending critical. Values of squeeze film damping coefficients obtained from measured data are compared to theoretical values obtained from short bearing approximation over a frequency range from 5000 to 31,000 cycles/min. Experimental response for an undamped rotor is compared to that of one having oil squeeze film dampers at the bearings. Unbalances applied varied from 0.62 to 15.1 gm-cm.

  11. Steady State Ocean Response to Wind Forcing in Extratropical Frontal Regions.

    PubMed

    Cronin, Meghan F; Tozuka, Tomoki

    2016-01-01

    In regions of strong sea surface temperature (SST) gradients, the surface "geostrophic" currents have a vertical shear aligned with the surface density front defined by the temperature. This surface geostrophic ("thermal wind") shear can balance a portion of the surface wind stress, altering the classic Ekman response to wind forcing. Here we show that these frontal effects cannot be ignored in the Tropics or in strong frontal regions in the extratropics, such as found in coastal regions and in western boundary currents of all basins. Frontal effects also dominate the classic Ekman response in the regions of both hemispheres where Trade winds change to westerlies. Implications for vertical motion and global heat transport are discussed. PMID:27354231

  12. Steady State Ocean Response to Wind Forcing in Extratropical Frontal Regions

    PubMed Central

    Cronin, Meghan F.; Tozuka, Tomoki

    2016-01-01

    In regions of strong sea surface temperature (SST) gradients, the surface “geostrophic” currents have a vertical shear aligned with the surface density front defined by the temperature. This surface geostrophic (“thermal wind”) shear can balance a portion of the surface wind stress, altering the classic Ekman response to wind forcing. Here we show that these frontal effects cannot be ignored in the Tropics or in strong frontal regions in the extratropics, such as found in coastal regions and in western boundary currents of all basins. Frontal effects also dominate the classic Ekman response in the regions of both hemispheres where Trade winds change to westerlies. Implications for vertical motion and global heat transport are discussed. PMID:27354231

  13. Steady-state response of a geared rotor system with slant cracked shaft and time-varying mesh stiffness

    NASA Astrophysics Data System (ADS)

    Han, Qinkai; Zhao, Jingshan; Lu, Wenxiu; Peng, Zhike; Chu, Fulei

    2014-04-01

    The dynamic behavior of geared rotor system with defects is helpful for the failure diagnosis and state detecting of the system. Extensive efforts have been devoted to study the dynamic behaviors of geared systems with tooth root cracks. When surface cracks (especially for slant cracks) appear on the transmission shaft, the dynamic characteristics of the system have not gained sufficient attentions. Due to the parametric excitations induced by slant crack breathing and time-varying mesh stiffness, the steady-state response of the cracked geared rotor system differs distinctly from that of the uncracked system. Thus, utilizing the direct spectral method (DSM), the forced response spectra of a geared rotor system with slant cracked shaft and time-varying mesh stiffness under transmission error, unbalance force and torsional excitations are, respectively, obtained and discussed in detail. The effects of crack types (straight or slant crack) and crack depth on the forced response spectra of the system without and with torsional excitation are considered in the analysis. In addition, how the frequency response characteristics change after considering the crack is also investigated. It is shown that the torsional excitations have significant influence on the forced response spectra of slant cracked system. Sub-critical resonances are also found in the frequency response curves. The results could be used for shaft crack detection in geared rotor system.

  14. Material Response of One-Dimensional, Steady-State Transpiration Cooling in Radiative and Convective Environments

    NASA Technical Reports Server (NTRS)

    Kubota, Hirotoshi

    1975-01-01

    A simplified analytical solution for thermal response of a transpiration-cooled porous heat-shield material in an intense radiative-convective heating environment is presented. Essential features of this approach are "two-flux method" for radiative transfer process and "two-temperature" assumption for solid and gas temperatures. Incident radiative-convective heatings are specified as boundary conditions. Sample results are shown using porous silica with CO2 transpiration and some parameters quantitatively show the effect on this transpiration cooling system. Summarized maps for mass injection rate, porosity and blowing correction factor for radiation are obtained in order to realize such a cooling system.

  15. Calibration and validation of a modified steady-state model of crop response to saline water irrigation under conditions of transient root zone salinity

    NASA Astrophysics Data System (ADS)

    Vinten, A. J. A.; Frenkel, H.; Shalhevet, J.; Elston, D. A.

    1991-01-01

    In many situations where annual crops are irrigated with saline water, root zone salinity does not reach a steady state. Use of a steady-state description of root zone salinity may then seriously overestimate the calculated leaching requirements of the crop. A steady-state semi-emphirical model of crop response to irrigation with saline water has been calibrated using data from a number of field experiments. Predictions of yield deficit resulting from irrigation with saline water have been made for each of these experiments, using both the original model and a modified version which allows for the non-steady-state salinity conditions occurring in the experiments. Comparison with experimental data shows a clear superiority of the modified version in most cases studied. Where the original model is superior or equally good, it is likely that steady-state conditions are being approached. Where root zone salinity data were available and applicable, the modified model predicted root zone salinity much better. Approaches for distinguishing errors in calibration from intrinsic errors in the model assumptions are discussed.

  16. Resistive wall mode feedback control in EXTRAP T2R with improved steady-state error and transient response

    SciTech Connect

    Brunsell, P. R.; Olofsson, K. E. J.; Frassinetti, L.; Drake, J. R.

    2007-10-15

    Experiments in the EXTRAP T2R reversed field pinch [P. R. Brunsell, H. Bergsa ring ker, M. Cecconello et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] on feedback control of m=1 resistive wall modes (RWMs) are compared with simulations using the cylindrical linear magnetohydrodynamic model, including the dynamics of the active coils and power amplifiers. Stabilization of the main RWMs (n=-11,-10,-9,-8,+5,+6) is shown using modest loop gains of the order G{approx}1. However, other marginally unstable RWMs (n=-2,-1,+1,+2) driven by external field errors are only partially canceled at these gains. The experimental system stability limit is confirmed by simulations showing that the latency of the digital controller {approx}50 {mu}s is degrading the system gain margin. The transient response is improved with a proportional-plus-derivative controller, and steady-state error is improved with a proportional-plus-integral controller. Suppression of all modes is obtained at high gain G{approx}10 using a proportional-plus-integral-plus-derivative controller.

  17. Coupled bending-torsion steady-state response of pretwisted, nonuniform rotating beams using a transfer-matrix method

    NASA Technical Reports Server (NTRS)

    Gray, Carl E., Jr.

    1988-01-01

    Using the Newtonian method, the equations of motion are developed for the coupled bending-torsion steady-state response of beams rotating at constant angular velocity in a fixed plane. The resulting equations are valid to first order strain-displacement relationships for a long beam with all other nonlinear terms retained. In addition, the equations are valid for beams with the mass centroidal axis offset (eccentric) from the elastic axis, nonuniform mass and section properties, and variable twist. The solution of these coupled, nonlinear, nonhomogeneous, differential equations is obtained by modifying a Hunter linear second-order transfer-matrix solution procedure to solve the nonlinear differential equations and programming the solution for a desk-top personal computer. The modified transfer-matrix method was verified by comparing the solution for a rotating beam with a geometric, nonlinear, finite-element computer code solution; and for a simple rotating beam problem, the modified method demonstrated a significant advantage over the finite-element solution in accuracy, ease of solution, and actual computer processing time required to effect a solution.

  18. Low frequency steady-state brain responses modulate large scale functional networks in a frequency-specific means.

    PubMed

    Wang, Yi-Feng; Long, Zhiliang; Cui, Qian; Liu, Feng; Jing, Xiu-Juan; Chen, Heng; Guo, Xiao-Nan; Yan, Jin H; Chen, Hua-Fu

    2016-01-01

    Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (<1 Hz). However, it is difficult to determine the frequency characteristics of brain networks because both resting-state studies and conventional frequency tagging approaches cannot simultaneously capture multiple large scale networks in controllable cognitive activities. In this preliminary study, we aimed to examine whether large scale networks can be modulated by task-induced low frequency steady-state brain responses (lfSSBRs) in a frequency-specific pattern. In a revised attention network test, the lfSSBRs were evoked in the triple network system and sensory-motor system, indicating that large scale networks can be modulated in a frequency tagging way. Furthermore, the inter- and intranetwork synchronizations as well as coherence were increased at the fundamental frequency and the first harmonic rather than at other frequency bands, indicating a frequency-specific modulation of information communication. However, there was no difference among attention conditions, indicating that lfSSBRs modulate the general attention state much stronger than distinguishing attention conditions. This study provides insights into the advantage and mechanism of lfSSBRs. More importantly, it paves a new way to investigate frequency-specific large scale brain activities. PMID:26512872

  19. Cell yields and fermentation responses of a Salmonella Typhimurium poultry isolate at different dilution rates in an anaerobic steady state continuous culture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objectives of these studies were to determine cell yield and fermentation responses of a Salmonella enterica serovar Typhimurium poultry isolate using various dilution rates in steady state continuous culture incubations. S. enterica Typhimurium cells were propagated in continuous cultures with ...

  20. An objective method for measuring face detection thresholds using the sweep steady-state visual evoked response.

    PubMed

    Ales, Justin M; Farzin, Faraz; Rossion, Bruno; Norcia, Anthony M

    2012-01-01

    We introduce a sensitive method for measuring face detection thresholds rapidly, objectively, and independently of low-level visual cues. The method is based on the swept parameter steady-state visual evoked potential (ssVEP), in which a stimulus is presented at a specific temporal frequency while parametrically varying ("sweeping") the detectability of the stimulus. Here, the visibility of a face image was increased by progressive derandomization of the phase spectra of the image in a series of equally spaced steps. Alternations between face and fully randomized images at a constant rate (3/s) elicit a robust first harmonic response at 3 Hz specific to the structure of the face. High-density EEG was recorded from 10 human adult participants, who were asked to respond with a button-press as soon as they detected a face. The majority of participants produced an evoked response at the first harmonic (3 Hz) that emerged abruptly between 30% and 35% phase-coherence of the face, which was most prominent on right occipito-temporal sites. Thresholds for face detection were estimated reliably in single participants from 15 trials, or on each of the 15 individual face trials. The ssVEP-derived thresholds correlated with the concurrently measured perceptual face detection thresholds. This first application of the sweep VEP approach to high-level vision provides a sensitive and objective method that could be used to measure and compare visual perception thresholds for various object shapes and levels of categorization in different human populations, including infants and individuals with developmental delay. PMID:23024355

  1. Monocular and binocular steady-state flicker VEPs: frequency-response functions to sinusoidal and square-wave luminance modulation.

    PubMed

    Nicol, David S; Hamilton, Ruth; Shahani, Uma; McCulloch, Daphne L

    2011-02-01

    Steady-state VEPs to full-field flicker (FFF) using sinusoidally modulated light were compared with those elicited by square-wave modulated light across a wide range of stimulus frequencies with monocular and binocular FFF stimulation. Binocular and monocular VEPs were elicited in 12 adult volunteers to FFF with two modes of temporal modulation: sinusoidal or square-wave (abrupt onset and offset, 50% duty cycle) at ten temporal frequencies ranging from 2.83 to 58.8 Hz. All stimuli had a mean luminance of 100 cd/m(2) with an 80% modulation depth (20-180 cd/m(2)). Response magnitudes at the stimulus frequency (F1) and at the double and triple harmonics (F2 and F3) were compared. For both sinusoidal and square-wave flicker, the FFF-VEP magnitudes at F1 were maximal for 7.52 Hz flicker. F2 was maximal for 5.29 Hz flicker, and F3 magnitudes are largest for flicker stimulation from 3.75 to 7.52 Hz. Square-wave flicker produced significantly larger F1 and F2 magnitudes for slow flicker rates (up to 5.29 Hz for F1; at 2.83 and 3.75 Hz for F2). The F3 magnitudes were larger overall for square-wave flicker. Binocular FFF-VEP magnitudes are larger than those of monocular FFF-VEPs, and the amount of this binocular enhancement is not dependant on the mode of flicker stimulation (mean binocular: monocular ratio 1.41, 95% CI: 1.2-1.6). Binocular enhancement of F1 for 21.3 Hz flicker was increased to a factor of 2.5 (95% CI: 1.8-3.5). In the healthy adult visual system, FFF-VEP magnitudes can be characterized by the frequency-response functions of F1, F2 and F3. Low-frequency roll-off in the FFF-VEP magnitudes is greater for sinusoidal flicker than for square-wave flicker for rates ≤ 5.29 Hz; magnitudes for higher-frequency flicker are similar for the two types of flicker. Binocular FFF-VEPs are larger overall than those recorded monocularly, and this binocular summation is enhanced at 21.3 Hz in the mid-frequency range. PMID:21279419

  2. Steady-state response of an elastic half space containing a point source of heat. Research report

    SciTech Connect

    Booker, J.R.; Carter, J.P.

    1985-08-01

    Closed form solutions are presented for the steady-state distributions of temperature, displacement, and stress around a point source of heat embedded in a homogeneous, isotropic elastic half space. These solutions were evaluated for a typical case of a heat source buried, in rock and quantities such as the heave of the ground surface and the maximum horizontal tensile stress at the surface estimated. The results may have applications in the fields of geothermal, geotechnical, nuclear, and petroleum engineering where the soil or rock might reasonably be modelled, at least in the first instance, as a linear thermoelastic material.

  3. Extrasolar Giant Magnetospheric Response to Steady-state Stellar Wind Pressure at 10, 5, 1, and 0.2 au

    NASA Astrophysics Data System (ADS)

    Tilley, Matt A.; Harnett, Erika M.; Winglee, Robert M.

    2016-08-01

    A three-dimensional, multifluid simulation of a giant planet’s magnetospheric interaction with steady-state stellar wind from a Sun-like star was performed for four different orbital semimajor axes—10, 5, 1, and 0.2 au. We simulate the effect of the increasing, steady-state stellar wind pressure related to the planetary orbital semimajor axis on the global magnetospheric dynamics for a Saturn-like planet, including an Enceladus-like plasma torus. Mass-loss processes are shown to vary with orbital distance, with the centrifugal interchange instability displayed only in the 10 and 5 au cases, which reach a state of mass-loss equilibrium more slowly than the 1 or 0.2 au cases. The compression of the magnetosphere in the 1 and 0.2 au cases contributes to the quenching of the interchange process by increasing the ratio of total plasma thermal energy to corotational energy. The strength of field-aligned currents, associated with auroral radio emissions, is shown to increase in magnitude and latitudinal coverage with a corresponding shift equatorward from increased dynamic ram pressure experienced in the hotter orbits. Similar to observed hot Jovian planets, the warm exo-Saturn simulated in the current work shows enhanced ion density in the magnetosheath and magnetopause regions, as well as the plasma torus, which could contribute to altered transit signals, suggesting that for planets in warmer (>0.1 au) orbits, planetary magnetic field strengths and possibly exomoons—via the plasma torus—could be observable with future missions.

  4. Non-steady-state measurement of in vivo receptor binding with positron emission tomography: Dose-response analysis

    SciTech Connect

    Perlmutter, J.S.; Kilbourn, M.R.; Welch, M.J.; Raichle, M.E. )

    1989-07-01

    We previously developed a non-steady-state technique using positron emission tomography (PET) and the radioligand 18F-spiperone (18F-SP) for the measurement of in vivo radioligand-receptor binding in brain. The purpose of this investigation is to determine the sensitivity of this method to alterations in the apparent number of available specific binding sites. Nine studies were performed on the same baboon. The animal was pretreated with varying doses of unlabeled SP (15-600 micrograms) to compete for specific binding sites. The experimental procedure included measurement of regional cerebral blood flow, cerebral blood volume, and the protein binding of 18F-SP in arterial blood. At least 3.5 hr after pretreatment, no-carrier-added 18F-SP (containing less than 3 micrograms SP) was administered intravenously. Sequential PET scans and measurements of arterial-blood radioactivity due to radioligand and its labeled metabolites continued for 3 hr. A 3-compartment model representing the in vivo behavior of radioligand was used to analyze the data. As expected, we found that an index of binding called the combined forward rate constant (which equals the product of the apparent maximum number of available specific binding sites and the association rate constant of radioligand for receptor) declined with increasing dose of unlabeled SP. Other estimated variables including the dissociation rate constant did not change. This demonstrates that our non-steady-state method for estimating radioligand-receptor binding kinetics can detect a decrease in the apparent number of available specific binding sites. This is an important step in the validation of this in vivo receptor binding assay and its subsequent application.

  5. Disruption of the auditory response to a regular click train by a single, extra click.

    PubMed

    Lütkenhöner, Bernd; Patterson, Roy D

    2015-06-01

    It has been hypothesized that the steady-state response to a periodic sequence of clicks can be modeled as the superposition of responses to single clicks. Here, this hypothesis is challenged by presenting an extra click halfway between two consecutive clicks of a regular series, while measuring the auditory evoked field. After a solitary click at time zero, the click series sounded from 100 to 900 ms, with the extra click presented around 500 ms. The silent period between two stimulus sequences was 310-390 ms (uniformly distributed) so that one stimulation cycle lasted, on average, 1250 ms. Five different click rates between 20 and 60 Hz were examined. The disturbance caused by the extra click was revealed by subtracting the estimated steady-state response from the joint response to the click series and the extra click. The early peaks of the single-click response effectively coincide with same-polarity peaks of the 20-Hz steady-state response. Nevertheless, prediction of the latter from the former proved impossible. However, the 40-Hz steady-state response can be predicted reasonably well from the 20-Hz steady-state response. Somewhat surprisingly, the amplitude of the evoked response to the extra click grew when the click rate of the train was increased from 20 to 30 Hz; the opposite effect would have been expected from research on adaptation. The smaller amplitude at lower click rates might be explained by forward suppression. In this case, the apparent escape from suppression at higher rates might indicate that the clicks belonging to the periodic train are being integrated into an auditory stream, possibly in much the same manner as in classical stream segregation experiments. PMID:25814380

  6. Psychophysiological responses to auditory change.

    PubMed

    Chuen, Lorraine; Sears, David; McAdams, Stephen

    2016-06-01

    A comprehensive characterization of autonomic and somatic responding within the auditory domain is currently lacking. We studied whether simple types of auditory change that occur frequently during music listening could elicit measurable changes in heart rate, skin conductance, respiration rate, and facial motor activity. Participants heard a rhythmically isochronous sequence consisting of a repeated standard tone, followed by a repeated target tone that changed in pitch, timbre, duration, intensity, or tempo, or that deviated momentarily from rhythmic isochrony. Changes in all parameters produced increases in heart rate. Skin conductance response magnitude was affected by changes in timbre, intensity, and tempo. Respiratory rate was sensitive to deviations from isochrony. Our findings suggest that music researchers interpreting physiological responses as emotional indices should consider acoustic factors that may influence physiology in the absence of induced emotions. PMID:26927928

  7. The human auditory evoked response

    NASA Technical Reports Server (NTRS)

    Galambos, R.

    1974-01-01

    Figures are presented of computer-averaged auditory evoked responses (AERs) that point to the existence of a completely endogenous brain event. A series of regular clicks or tones was administered to the ear, and 'odd-balls' of different intensity or frequency respectively were included. Subjects were asked either to ignore the sounds (to read or do something else) or to attend to the stimuli. When they listened and counted the odd-balls, a P3 wave occurred at 300msec after stimulus. When the odd-balls consisted of omitted clicks or tone bursts, a similar response was observed. This could not have come from auditory nerve, but only from cortex. It is evidence of recognition, a conscious process.

  8. The effects of boundary conditions on the steady-state response of three hypothetical ground-water systems; results and implications of numerical experiments

    USGS Publications Warehouse

    Franke, O. Lehn; Reilly, Thomas E.

    1987-01-01

    The most critical and difficult aspect of defining a groundwater system or problem for conceptual analysis or numerical simulation is the selection of boundary conditions . This report demonstrates the effects of different boundary conditions on the steady-state response of otherwise similar ground-water systems to a pumping stress. Three series of numerical experiments illustrate the behavior of three hypothetical groundwater systems that are rectangular sand prisms with the same dimensions but with different combinations of constant-head, specified-head, no-flow, and constant-flux boundary conditions. In the first series of numerical experiments, the heads and flows in all three systems are identical, as are the hydraulic conductivity and system geometry . However, when the systems are subjected to an equal stress by a pumping well in the third series, each differs significantly in its response . The highest heads (smallest drawdowns) and flows occur in the systems most constrained by constant- or specified-head boundaries. These and other observations described herein are important in steady-state calibration, which is an integral part of simulating many ground-water systems. Because the effects of boundary conditions on model response often become evident only when the system is stressed, a close match between the potential distribution in the model and that in the unstressed natural system does not guarantee that the model boundary conditions correctly represent those in the natural system . In conclusion, the boundary conditions that are selected for simulation of a ground-water system are fundamentally important to groundwater systems analysis and warrant continual reevaluation and modification as investigation proceeds and new information and understanding are acquired.

  9. Analysis of high field effects on the steady-state current-voltage response of semi-insulating 4H-SiC for photoconductive switch applications

    SciTech Connect

    Tiskumara, R.; Joshi, R. P. Mauch, D.; Dickens, J. C.; Neuber, A. A.

    2015-09-07

    A model-based analysis of the steady-state, current-voltage response of semi-insulating 4H-SiC is carried out to probe the internal mechanisms, focusing on electric field driven effects. Relevant physical processes, such as multiple defects, repulsive potential barriers to electron trapping, band-to-trap impact ionization, and field-dependent detrapping, are comprehensively included. Results of our model match the available experimental data fairly well over orders of magnitude variation in the current density. A number of important parameters are also extracted in the process through comparisons with available data. Finally, based on our analysis, the possible presence of holes in the samples can be discounted up to applied fields as high as ∼275 kV/cm.

  10. Influence of oil-squeeze-film damping on steady-state response of flexible rotor operating to supercritical speeds

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1977-01-01

    Experimental data were obtained for the unbalance response of a flexible rotor to speeds above the third lateral bending critical. Squeeze-film damping coefficients calculated from measured data showed good agreement with short-journal-bearing approximations over a frequency range from 5000 to 31,000 cmp. Response of a rotor to varying amounts of unbalance was investigated. A very lightly damped rotor was compared with one where oil-squeeze dampers were applied.

  11. Steady State Dense Gas Dispersion

    Energy Science and Technology Software Center (ESTSC)

    1995-03-01

    SLAB-LLNL is a steady-state one-dimensional program which calculates the atmospheric dispersion of a heavier than air gas that is continuously released at ground level. The model is based on the steady-state crosswind-averaged conservation equations of species, mass, energy, and momentum. It uses the air entrainment concept to account for the turbulent mixing of the gas cloud with the surrounding atmosphere and similarity profiles to determine the crosswind dependence.

  12. Auditory-pupillary responses in deaf subjects.

    PubMed

    Kitajima, Naoharu; Otsuka, Koji; Ogawa, Yasuo; Shimizu, Shigetaka; Hayashi, Mami; Ichimura, Akihide; Suzuki, Mamoru

    2010-01-01

    Pupillary dilation in response to sound stimuli is well established and is generally considered to represent a startle reflex to sound. We believe that the auditory-pupillary response represents not only a simple startle reflex to sound stimuli but also represents a reaction to stimulation of other sense organs, such as otolith organs. Eight young healthy volunteers without a history of hearing and equilibrium problems and 12 subjects with bilateral deafness participated in this study. Computer pupillography was used to analyze the auditory-pupillary responses of both eyes in all subjects. We found that auditory-pupillary responses occurred even in subjects with bilateral deafness and that this response was comparable to those of normal subjects. We propose that the auditory-pupillary response also relates to vestibular function. Thus, assessing the auditory-pupillary response may be useful for evaluating the vestibulo-autonomic response in patients with peripheral disequilibrium. PMID:20826936

  13. Estradiol promotes functional responses in inflammatory and steady-state dendritic cells through differential requirement for activation function-1 of estrogen receptor α.

    PubMed

    Seillet, Cyril; Rouquié, Nelly; Foulon, Eliane; Douin-Echinard, Victorine; Krust, Andrée; Chambon, Pierre; Arnal, Jean-François; Guéry, Jean-Charles; Laffont, Sophie

    2013-06-01

    17β-Estradiol (E2) has been shown to regulate GM-CSF- or Flt3 ligand-driven dendritic cell (DC) development through estrogen receptor (ER) α signaling in myeloid progenitors. ERα regulates transcription of target genes through two distinct activation functions (AFs), AF-1 and AF-2, whose respective involvement varies in a cell type- or tissue-specific manner. In this study, we investigated the role of ERα AFs in the development and effector functions of inflammatory DCs, steady-state conventional DCs, and plasmacytoid DCs (pDC), using mouse lacking either AF-1 or AF-2. In agreement with previous works, we showed that E2 fostered the differentiation and effector functions of inflammatory DCs through ERα-dependent upregulation of IFN regulatory factor (IRF)-4 in GM-CSF-stimulated myeloid progenitors. Interestingly, whereas AF-1 was required for early IRF-4 upregulation in DC precursors, it was dispensable to enhance IRF-4 expression in differentiated DCs to a level compatible with the development of the more functional Ly6C(-) CD11b(+) DC subset. Presence of E2 had no effect on progenitors from either knock-in mice with 7-aa deletion in helix 12 of ERα, lacking AF-2, or ERα(-/-) mice. By contrast, in Flt3 ligand-driven DC differentiation, activation of AF-1 domain was required to promote the development of more functionally competent conventional DCs and pDCs. Moreover, lack of ERα AF-1 blunted the TLR7-mediated IFN-α response of female pDCs in vivo. Thus, our study demonstrates that ERα uses AF-1 differently in steady-state and inflammatory DC lineages to regulate their innate functions, suggesting that selective ER modulators could be used to target specific DC subsets. PMID:23626011

  14. [Hypercapnic stimulation and ventilation response in the syndrome of sleep obstructive apnea. Comparison of reinhalation and steady state].

    PubMed

    Soto Campos, J G; Cano Gómez, S; Fernández Guerra, J; Sánchez Armengol, M; Capote Gil, F; Castillo Gómez, J

    1996-01-01

    The objective of this study was to assess ventilatory response to stimulation with CO2 in patients suffering obstructive sleep apnea syndrome (OSAS) but without chronic obstructive pulmonary disease (COPD), by examining differences between hyper- and normocapnic patients and comparing the results obtained with the usual techniques used to stimulate hypercapnia (rebreathing and stable-state). To this end, we studied 15 obese patients, all with an apnea-hypopnea index greater than 10 from a polysomnograph lasting a full night. The following lung function tests were performed: spirometry, air way resistance measures and static lung volumes by plethysmograph and arterial gasometry. We later analyzed ventilatory response by the stable-state method, with increasing CO2 concentrations (from 1 to 9%) and by the rebreathing method. Results from the two methods were similar for all patients: delta VE/delta PCO2 (0.64 +/- 0.35 vs 0.67 +/- 0.48 l/min/mmHg; p = 0.59), delta Vt/delta PCO2 (28.33 +/- 16.23 vs 26.42 +/- 16.94 ml/mmHg; p = 0.9), delta Vt/Ti/delta PCO2 (28.82 +/- 20.9 vs 29.41 +/- 23.78 ml/s/mmHg; p = 0.89) y delta P0.1/delta PCO2 (0.11 +/- 0.07 vs 0.117 +/- 0.05 cmH2O/mmHg; p = 0.58). We compared the results obtained by the two techniques by dividing the sample into two groups of 7 and 8 patients, respectively, depending on whether PaCO2 level before stimulation was higher or lower than 45 mmHg. The hypercapnic patients (group I) were older (61 +/- 3.5 vs 50 +/- 9 years; p = 0.04) but were not different with respect to body mass from the normocapnic patients (group II) (37.59 +/- 6.4 vs 34.56 +/- 4.75 kg/m2; p = 0.33). The results from the two techniques for stimulating hypercapnia were similar within each group, with a statistically significant decrease (p < 0.03) in patients with daytime hypercapnia in delta VE/delta PCO2 delta Vt/delta PCO2, delta Vt/Ti/delta PCO2 and delta P0.1/delta PCO2. We conclude that there are no differences in the results obtained with

  15. Behavioral Dependence of Auditory Cortical Responses

    PubMed Central

    Osmanski, Michael S.; Wang, Xiaoqin

    2015-01-01

    Neural responses in the auditory cortex have historically been measured from either anesthetized or awake but non-behaving animals. A growing body of work has begun to focus instead on recording from auditory cortex of animals actively engaged in behavior tasks. These studies have shown that auditory cortical responses are dependent upon the behavioral state of the animal. The longer ascending subcortical pathway of the auditory system and unique characteristics of auditory processing suggest that such dependencies may have a more profound influence on cortical processing in auditory system compared to other sensory systems. It is important to understand the nature of these dependencies and their functional implications. In this article, we review the literature on this topic pertaining to cortical processing of sounds. PMID:25690831

  16. Steady-state response attenuation of a linear oscillator-nonlinear absorber system by using an adjustable-length pendulum in series: Numerical and experimental results

    NASA Astrophysics Data System (ADS)

    Eason, R. P.; Sun, C.; Dick, A. J.; Nagarajaiah, S.

    2015-05-01

    Response attenuation of a linear primary structure (PS)-nonlinear tuned mass damper (NTMD) dynamic system with and without an adaptive-length pendulum tuned mass damper (ALPTMD) in a series configuration is studied by using numerical and experimental methods. In the PS-NTMD system, coexisting high and low amplitude solutions are observed in the experiment, validating previous numerical efforts. In order to eliminate the potentially dangerous high amplitude solutions, a series ALPTMD with a mass multiple orders of magnitude smaller than the PS is added to the NTMD. The ALPTMD is used in order to represent the steady-state behavior of a smart tuned mass damper (STMD). In the experiment, the length of the pendulum is adjusted such that its natural frequency matches the dominant frequency of the harmonic ground motions. In the present study, the proposed ALPTMD can be locked so that it is unable to oscillate and influence the dynamics of the system in order to obtain the benefits provided by the NTMD. The experimental data show good qualitative agreement with numerical predictions computed with parameter continuation and time integration methods. Activation of the ALPTMD can successfully prevent the transition of the response from the low amplitude solution to the high amplitude solution or return the response from the high amplitude solution to the low amplitude solution, thereby protecting the PS.

  17. Staffing in a Steady State.

    ERIC Educational Resources Information Center

    Owens, J. A.

    1982-01-01

    Options for faculty utilization in a steady state are examined, with consideration for their economy or ability to increase turnover or flexibility: early retirement, part retirement, retraining, exchange with other institutions or industry, and fixed-term appointments or lecturer positions. (MSE)

  18. Corticofugal modulation of peripheral auditory responses

    PubMed Central

    Terreros, Gonzalo; Delano, Paul H.

    2015-01-01

    The auditory efferent system originates in the auditory cortex and projects to the medial geniculate body (MGB), inferior colliculus (IC), cochlear nucleus (CN) and superior olivary complex (SOC) reaching the cochlea through olivocochlear (OC) fibers. This unique neuronal network is organized in several afferent-efferent feedback loops including: the (i) colliculo-thalamic-cortico-collicular; (ii) cortico-(collicular)-OC; and (iii) cortico-(collicular)-CN pathways. Recent experiments demonstrate that blocking ongoing auditory-cortex activity with pharmacological and physical methods modulates the amplitude of cochlear potentials. In addition, auditory-cortex microstimulation independently modulates cochlear sensitivity and the strength of the OC reflex. In this mini-review, anatomical and physiological evidence supporting the presence of a functional efferent network from the auditory cortex to the cochlear receptor is presented. Special emphasis is given to the corticofugal effects on initial auditory processing, that is, on CN, auditory nerve and cochlear responses. A working model of three parallel pathways from the auditory cortex to the cochlea and auditory nerve is proposed. PMID:26483647

  19. Study on steady-state response of a vertical axis automatic washing machine with a hydraulic balancer using a new approach and a method for getting a smaller deflection angle

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Wei; Zhang, Qiu-Ju; Fan, Sheng-Yao

    2011-04-01

    A new approach is used in this paper to analyze steady-state response of a vertical axis automatic washing machine with a hydraulic balancer and a method for getting a smaller deflection angle of the washing/drying assembly is presented. First, a mathematical model of the vertical axis washing machine and a numerical description of the hydraulic balancer are described and a vibration model for the vertical axis washing machine with a hydraulic balancer is built. Second, the vibration model is transformed into an autonomous form whose equilibrium point can be used to analyze dynamics of the washing machine at the steady state. Because the autonomous form can be solved by the Newton-Raphson method which requires only a few iterations, it provides a much faster approach for analyzing steady-state response of the spin drying process than traditional numerical integration methods. Five parameters influencing the spin drying process are considered, and the balancer's importance in reducing vibrations at the steady state is illustrated. Third, the equilibrium conditions of the centrifugal forces acting on the clothes, the washing/drying assembly and the balancer are considered, and a governing equation for getting a smaller deflection angle of the washing/drying assembly is derived. At last, parameters in the governing equation, especially those related to the hydraulic balancer, are discussed.

  20. On Typicality in Nonequilibrium Steady States

    NASA Astrophysics Data System (ADS)

    Evans, Denis J.; Williams, Stephen R.; Searles, Debra J.; Rondoni, Lamberto

    2016-06-01

    From the statistical mechanical viewpoint, relaxation of macroscopic systems and response theory rest on a notion of typicality, according to which the behavior of single macroscopic objects is given by appropriate ensembles: ensemble averages of observable quantities represent the measurements performed on single objects, because "almost all" objects share the same fate. In the case of non-dissipative dynamics and relaxation toward equilibrium states, "almost all" is referred to invariant probability distributions that are absolutely continuous with respect to the Lebesgue measure. In other words, the collection of initial micro-states (single systems) that do not follow the ensemble is supposed to constitute a set of vanishing, phase space volume. This approach is problematic in the case of dissipative dynamics and relaxation to nonequilibrium steady states, because the relevant invariant distributions attribute probability 1 to sets of zero volume, while evolution commonly begins in equilibrium states, i.e., in sets of full phase space volume. We consider the relaxation of classical, thermostatted particle systems to nonequilibrium steady states. We show that the dynamical condition known as Ω T-mixing is necessary and sufficient for relaxation of ensemble averages to steady state values. Moreover, we find that the condition known as weak T-mixing applied to smooth observables is sufficient for ensemble relaxation to be independent of the initial ensemble. Lastly, we show that weak T-mixing provides a notion of typicality for dissipative dynamics that is based on the (non-invariant) Lebesgue measure, and that we call physical ergodicity.

  1. On Typicality in Nonequilibrium Steady States

    NASA Astrophysics Data System (ADS)

    Evans, Denis J.; Williams, Stephen R.; Searles, Debra J.; Rondoni, Lamberto

    2016-08-01

    From the statistical mechanical viewpoint, relaxation of macroscopic systems and response theory rest on a notion of typicality, according to which the behavior of single macroscopic objects is given by appropriate ensembles: ensemble averages of observable quantities represent the measurements performed on single objects, because " almost all" objects share the same fate. In the case of non-dissipative dynamics and relaxation toward equilibrium states, " almost all" is referred to invariant probability distributions that are absolutely continuous with respect to the Lebesgue measure. In other words, the collection of initial micro-states (single systems) that do not follow the ensemble is supposed to constitute a set of vanishing, phase space volume. This approach is problematic in the case of dissipative dynamics and relaxation to nonequilibrium steady states, because the relevant invariant distributions attribute probability 1 to sets of zero volume, while evolution commonly begins in equilibrium states, i.e., in sets of full phase space volume. We consider the relaxation of classical, thermostatted particle systems to nonequilibrium steady states. We show that the dynamical condition known as Ω T-mixing is necessary and sufficient for relaxation of ensemble averages to steady state values. Moreover, we find that the condition known as weak T-mixing applied to smooth observables is sufficient for ensemble relaxation to be independent of the initial ensemble. Lastly, we show that weak T-mixing provides a notion of typicality for dissipative dynamics that is based on the (non-invariant) Lebesgue measure, and that we call physical ergodicity.

  2. Inconsistencies in steady state thermodynamics

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald; Motai, Ricardo

    2014-03-01

    We address the issue of extending thermodynamics to nonequilibrium steady states. Using driven stochastic lattice gases, we ask whether consistent definitions of an effective chemical potential μ, and an effective temperature Te, are possible. These quantities are determined via zero-flux conditions of particles and energy between the driven system and a reservoir. For the models considered here, the fluxes are given in terms of certain stationary average densities, eliminating the need to perturb the system by actually exchanging particles; μ and Te are thereby obtained via open-circuit measurements, using a virtual reservoir. In the lattice gas with nearest-neighbor exclusion, temperature is not relevant, and we find that the effective chemical potential, a function of density and drive strength, satisfies the zeroth law, and correctly predicts the densities of coexisting systems. In the Katz-Lebowitz-Spohn driven lattice gas, both μ and Te need to be defined. We show analytically that the zeroth law is violated, and determine the size of the violations numerically. Our results highlight a fundamental inconsistency in the extension of thermodynamics to nonequilibrium steady states. Research supported by CNPq, Brazil.

  3. Measurement of non-steady-state free fatty acid turnover

    SciTech Connect

    Jensen, M.D.; Heiling, V.; Miles, J.M. )

    1990-01-01

    The accuracy of non-steady-state equations for measuring changes in free fatty acid rate of appearance (Ra) is unknown. In the present study, endogenous lipolysis (traced with ({sup 14}C)-linoleate) was pharmacologically suppressed in six conscious mongrel dogs. A computer-responsive infusion pump was then used to deliver an intravenous oleic acid emulsion in both constant and linear gradient infusion modes. Both non-steady-state equations with various effective volumes of distribution (V) and steady-state equations were used to measure oleate Ra (({sup 14}C)oleate). Endogenous lipolysis did not change during the experiment. When oleate Ra increased in a linear gradient fashion, only non-steady-state equations with a large (150 ml/kg) V resulted in erroneous values (9% overestimate, P less than 0.05). In contrast, when oleate Ra decreased in a similar fashion, steady-state and standard non-steady-state equations (V = plasma volume = 50 ml/kg) overestimated total oleate Ra (18 and 7%, P less than 0.001 and P less than 0.05, respectively). Overall, non-steady-state equations with an effective V of 90 ml/kg (1.8 x plasma volume) allowed the most accurate estimates of oleate Ra.

  4. Irreversible processes at nonequilibrium steady states

    PubMed Central

    Fox, Ronald Forrest

    1979-01-01

    It is shown that a Liapunov criterion exists for the stability of nonequilibrium steady states. This criterion is based upon the fluctuation-dissipation relation, as was first pointed out by Keizer. At steady states, the Liapunov function is constructed from the covariance matrix for the thermodynamic variables. Unlike the situation around equilibrium, at steady states the covariance matrix and the “excess entropy” matrix are not equivalent. The excess entropy, which serves as the Liapunov function around equilibrium, does not work in this capacity at steady states. Keizer's Liapunov function must be viewed as the first correct candidate for a proper Liapunov function for steady states. PMID:16592649

  5. Visual modulation of auditory responses in the owl inferior colliculus.

    PubMed

    Bergan, Joseph F; Knudsen, Eric I

    2009-06-01

    The barn owl's central auditory system creates a map of auditory space in the external nucleus of the inferior colliculus (ICX). Although the crucial role visual experience plays in the formation and maintenance of this auditory space map is well established, the mechanism by which vision influences ICX responses remains unclear. Surprisingly, previous experiments have found that in the absence of extensive pharmacological manipulation, visual stimuli do not drive neural responses in the ICX. Here we investigated the influence of dynamic visual stimuli on auditory responses in the ICX. We show that a salient visual stimulus, when coincident with an auditory stimulus, can modulate auditory responses in the ICX even though the same visual stimulus may elicit no neural responses when presented alone. For each ICX neuron, the most effective auditory and visual stimuli were located in the same region of space. In addition, the magnitude of the visual modulation of auditory responses was dependent on the context of the stimulus presentation with novel visual stimuli eliciting consistently larger response modulations than frequently presented visual stimuli. Thus the visual modulation of ICX responses is dependent on the characteristics of the visual stimulus as well as on the spatial and temporal correspondence of the auditory and visual stimuli. These results demonstrate moment-to-moment visual enhancements of auditory responsiveness that, in the short-term, increase auditory responses to salient bimodal stimuli and in the long-term could serve to instruct the adaptive auditory plasticity necessary to maintain accurate auditory orienting behavior. PMID:19321633

  6. Auditory Brainstem Responses in Childhood Psychosis.

    ERIC Educational Resources Information Center

    Gillberg, Christopher; And Others

    1983-01-01

    Auditory brainstem responses (ABR) were compared in 24 autistic children, seven children with other childhood psychoses, and 31 normal children. One-third of the autistic Ss showed abnormal ABR indicating brainstem dysfunction and correlating with muscular hypotonia and severe language impairment. Ss with other psychoses and normal Ss showed…

  7. Articulatory movements modulate auditory responses to speech

    PubMed Central

    Agnew, Z.K.; McGettigan, C.; Banks, B.; Scott, S.K.

    2013-01-01

    Production of actions is highly dependent on concurrent sensory information. In speech production, for example, movement of the articulators is guided by both auditory and somatosensory input. It has been demonstrated in non-human primates that self-produced vocalizations and those of others are differentially processed in the temporal cortex. The aim of the current study was to investigate how auditory and motor responses differ for self-produced and externally produced speech. Using functional neuroimaging, subjects were asked to produce sentences aloud, to silently mouth while listening to a different speaker producing the same sentence, to passively listen to sentences being read aloud, or to read sentences silently. We show that that separate regions of the superior temporal cortex display distinct response profiles to speaking aloud, mouthing while listening, and passive listening. Responses in anterior superior temporal cortices in both hemispheres are greater for passive listening compared with both mouthing while listening, and speaking aloud. This is the first demonstration that articulation, whether or not it has auditory consequences, modulates responses of the dorsolateral temporal cortex. In contrast posterior regions of the superior temporal cortex are recruited during both articulation conditions. In dorsal regions of the posterior superior temporal gyrus, responses to mouthing and reading aloud were equivalent, and in more ventral posterior superior temporal sulcus, responses were greater for reading aloud compared with mouthing while listening. These data demonstrate an anterior–posterior division of superior temporal regions where anterior fields are suppressed during motor output, potentially for the purpose of enhanced detection of the speech of others. We suggest posterior fields are engaged in auditory processing for the guidance of articulation by auditory information. PMID:22982103

  8. Venusian hydrology: Steady state reconsidered

    NASA Technical Reports Server (NTRS)

    Grinspoon, David H.

    1992-01-01

    In 1987, Grinspoon proposed that the data on hydrogen abundance, isotopic composition, and escape rate were consistent with the hypothesis that water on Venus might be in steady state rather than monotonic decline since the dawn of time. This conclusion was partially based on a derived water lifetime against nonthermal escape of approximately 10(exp 8) yr. De Bergh et al., preferring the earlier Pioneer Venus value of 200 ppm water to the significantly lower value detected by Bezard et al., found H2O lifetimes of greater than 10(exp 9) yr. Donahue and Hodges derived H2O lifetimes of 0.4-5 x 10 (exp 9) yr. Both these analyses used estimates of H escape flux between 0.4 x 10(exp 7) and 1 x 10(exp 7) cm(exp -2)s(exp -1) from Rodriguez et al. Yet in more recent Monte Carlo modeling, Hodges and Tinsley found an escape flux due to charge exchange with hot H(+) of 2.8 x 10(exp 7) cm(exp -2)s(exp -1). McElroy et al. estimated an escape flux of 8 x 10(exp 6) cm(exp -2)s(exp -1) from collisions with hot O produced by dissociative recombination of O2(+). Brace et al. estimated an escape flux of 5 x 10(exp 6) cm(exp -2)s(exp -1) from ion escape from the ionotail of Venus. The combined estimated escape flux from all these processes is approximately 4 x 10(exp 7) cm(exp -2)s(exp -1). The most sophisticated analysis to date of near-IR radiation from Venus' nightside reveals a water mixing ratio of approximately 30 ppm, suggesting a lifetime against escape for water of less than 10(exp 8) yr. Large uncertainties remain in these quantities, yet the data point toward a steady state. Further evaluation of these uncertainties, and new evolutionary modeling incorporating estimates of the outgassing rate from post-Magellan estimates of the volcanic resurfacing rate are presented.

  9. Steady-State Response of the Flexible Connecting Rod of a Slider-Crank Mechanism with Time-Dependent Boundary Condition

    NASA Astrophysics Data System (ADS)

    Fung, R.-F.; Chen, H.-H.

    1997-01-01

    This paper presents a finite element method for the dynamic analysis of a flexible connecting rod in a slider-crank mechanism with time-dependent boundary conditions. Kinetic and strain energies of the flexible link are formulated and used with Hamilton's principle to develop the governing equations. Time-dependent boundary conditions instead of simply-supported end conditions are used to define the displacement field of the connecting rod. A special finite element method is developed for such a time-dependent boundary condition. The equations of motion are transformed into a set of ordinary differential equations and the harmonic balance method is used to obtain the steady-state amplitudes and rotary angles. The results are compared for the time dependent and simply-supported end conditions.

  10. Auditory Brainstem Response Improvements in Hyperbillirubinemic Infants

    PubMed Central

    Abdollahi, Farzaneh Zamiri; Manchaiah, Vinaya; Lotfi, Yones

    2016-01-01

    Background and Objectives Hyperbillirubinemia in infants have been associated with neuronal damage including in the auditory system. Some researchers have suggested that the bilirubin-induced auditory neuronal damages may be temporary and reversible. This study was aimed at investigating the auditory neuropathy and reversibility of auditory abnormalities in hyperbillirubinemic infants. Subjects and Methods The study participants included 41 full term hyperbilirubinemic infants (mean age 39.24 days) with normal birth weight (3,200-3,700 grams) that admitted in hospital for hyperbillirubinemia and 39 normal infants (mean age 35.54 days) without any hyperbillirubinemia or other hearing loss risk factors for ruling out maturational changes. All infants in hyperbilirubinemic group had serum bilirubin level more than 20 milligram per deciliter and undergone one blood exchange transfusion. Hearing evaluation for each infant was conducted twice: the first one after hyperbilirubinemia treatment and before leaving hospital and the second one three months after the first hearing evaluation. Hearing evaluations included transient evoked otoacoustic emission (TEOAE) screening and auditory brainstem response (ABR) threshold tracing. Results The TEOAE and ABR results of control group and TEOAE results of the hyperbilirubinemic group did not change significantly from the first to the second evaluation. However, the ABR results of the hyperbilirubinemic group improved significantly from the first to the second assessment (p=0.025). Conclusions The results suggest that the bilirubin induced auditory neuronal damage can be reversible over time so we suggest that infants with hyperbilirubinemia who fail the first hearing tests should be reevaluated after 3 months of treatment. PMID:27144228

  11. Neurodynamics, tonality, and the auditory brainstem response.

    PubMed

    Large, Edward W; Almonte, Felix V

    2012-04-01

    Tonal relationships are foundational in music, providing the basis upon which musical structures, such as melodies, are constructed and perceived. A recent dynamic theory of musical tonality predicts that networks of auditory neurons resonate nonlinearly to musical stimuli. Nonlinear resonance leads to stability and attraction relationships among neural frequencies, and these neural dynamics give rise to the perception of relationships among tones that we collectively refer to as tonal cognition. Because this model describes the dynamics of neural populations, it makes specific predictions about human auditory neurophysiology. Here, we show how predictions about the auditory brainstem response (ABR) are derived from the model. To illustrate, we derive a prediction about population responses to musical intervals that has been observed in the human brainstem. Our modeled ABR shows qualitative agreement with important features of the human ABR. This provides a source of evidence that fundamental principles of auditory neurodynamics might underlie the perception of tonal relationships, and forces reevaluation of the role of learning and enculturation in tonal cognition. PMID:22974442

  12. Response recovery in the locust auditory pathway.

    PubMed

    Wirtssohn, Sarah; Ronacher, Bernhard

    2016-01-01

    Temporal resolution and the time courses of recovery from acute adaptation of neurons in the auditory pathway of the grasshopper Locusta migratoria were investigated with a response recovery paradigm. We stimulated with a series of single click and click pair stimuli while performing intracellular recordings from neurons at three processing stages: receptors and first and second order interneurons. The response to the second click was expressed relative to the single click response. This allowed the uncovering of the basic temporal resolution in these neurons. The effect of adaptation increased with processing layer. While neurons in the auditory periphery displayed a steady response recovery after a short initial adaptation, many interneurons showed nonlinear effects: most prominent a long-lasting suppression of the response to the second click in a pair, as well as a gain in response if a click was preceded by a click a few milliseconds before. Our results reveal a distributed temporal filtering of input at an early auditory processing stage. This set of specified filters is very likely homologous across grasshopper species and thus forms the neurophysiological basis for extracting relevant information from a variety of different temporal signals. Interestingly, in terms of spike timing precision neurons at all three processing layers recovered very fast, within 20 ms. Spike waveform analysis of several neuron types did not sufficiently explain the response recovery profiles implemented in these neurons, indicating that temporal resolution in neurons located at several processing layers of the auditory pathway is not necessarily limited by the spike duration and refractory period. PMID:26609115

  13. 21 CFR 882.1900 - Evoked response auditory stimulator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Evoked response auditory stimulator. 882.1900 Section 882.1900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... auditory stimulator. (a) Identification. An evoked response auditory stimulator is a device that produces...

  14. 21 CFR 882.1900 - Evoked response auditory stimulator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Evoked response auditory stimulator. 882.1900 Section 882.1900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... auditory stimulator. (a) Identification. An evoked response auditory stimulator is a device that produces...

  15. On the time to steady state: insights from numerical modeling

    NASA Astrophysics Data System (ADS)

    Goren, L.; Willett, S.; McCoy, S. W.; Perron, J.

    2013-12-01

    How fast do fluvial landscapes approach steady state after an application of tectonic or climatic perturbation? While theory and some numerical models predict that the celerity of the advective wave (knickpoint) controls the response time for perturbations, experiments and other landscape evolution models demonstrate that the time to steady state is much longer than the theoretically predicted response time. We posit that the longevity of transient features and the time to steady state are controlled by the stability of the topology and geometry of channel networks. Evolution of a channel network occurs by a combination of discrete capture events and continuous migration of water divides, processes, which are difficult to represent accurately in landscape evolution models. We therefore address the question of the time to steady state using the DAC landscape evolution model that solves accurately for the location of water divides, using a combination of analytical solution for hillslopes and low-order channels together with a numerical solution for higher order channels. DAC also includes an explicit capture criterion. We have tested fundamental predictions from DAC and show that modeled networks reproduce natural network characteristics such as the Hack's exponent and coefficient and the fractal dimension. We define two steady-state criteria: a topographic steady state, defined by global, pointwise steady elevation, and a topological steady state defined as the state in which no further reorganization of the drainage network takes place. Analyzing block uplift simulations, we find that the time to achieve either topographic or topological steady state exceeds by an order of magnitude the theoretical response time of the fluvial network. The longevity of the transient state is the result of the area feedback, by which, migration of a divide changes the local contributing area. This change propagates downstream as a slope adjustment, forcing further divide migrations

  16. Auditory response to pulsed radiofrequency energy.

    PubMed

    Elder, J A; Chou, C K

    2003-01-01

    The human auditory response to pulses of radiofrequency (RF) energy, commonly called RF hearing, is a well established phenomenon. RF induced sounds can be characterized as low intensity sounds because, in general, a quiet environment is required for the auditory response. The sound is similar to other common sounds such as a click, buzz, hiss, knock, or chirp. Effective radiofrequencies range from 2.4 to 10000 MHz, but an individual's ability to hear RF induced sounds is dependent upon high frequency acoustic hearing in the kHz range above about 5 kHz. The site of conversion of RF energy to acoustic energy is within or peripheral to the cochlea, and once the cochlea is stimulated, the detection of RF induced sounds in humans and RF induced auditory responses in animals is similar to acoustic sound detection. The fundamental frequency of RF induced sounds is independent of the frequency of the radiowaves but dependent upon head dimensions. The auditory response has been shown to be dependent upon the energy in a single pulse and not on average power density. The weight of evidence of the results of human, animal, and modeling studies supports the thermoelastic expansion theory as the explanation for the RF hearing phenomenon. RF induced sounds involve the perception via bone conduction of thermally generated sound transients, that is, audible sounds are produced by rapid thermal expansion resulting from a calculated temperature rise of only 5 x 10(-6) degrees C in tissue at the threshold level due to absorption of the energy in the RF pulse. The hearing of RF induced sounds at exposure levels many orders of magnitude greater than the hearing threshold is considered to be a biological effect without an accompanying health effect. This conclusion is supported by a comparison of pressure induced in the body by RF pulses to pressure associated with hazardous acoustic energy and clinical ultrasound procedures. PMID:14628312

  17. Steady State Tokamak Equilibria without Current Drive

    SciTech Connect

    Shaing, K.C.; Aydemir, A.Y.; Lin-Liu, Y.R.; Miller, R.L.

    1997-11-01

    Steady state tokamak equilibria without current drive are found. This is made possible by including the potato bootstrap current close to the magnetic axis. Tokamaks with this class of equilibria do not need seed current or current drive, and are intrinsically steady state. {copyright} {ital 1997} {ital The American Physical Society}

  18. Relationship between Sympathetic Skin Responses and Auditory Hypersensitivity to Different Auditory Stimuli

    PubMed Central

    Kato, Fumi; Iwanaga, Ryoichiro; Chono, Mami; Fujihara, Saori; Tokunaga, Akiko; Murata, Jun; Tanaka, Koji; Nakane, Hideyuki; Tanaka, Goro

    2014-01-01

    [Purpose] Auditory hypersensitivity has been widely reported in patients with autism spectrum disorders. However, the neurological background of auditory hypersensitivity is currently not clear. The present study examined the relationship between sympathetic nervous system responses and auditory hypersensitivity induced by different types of auditory stimuli. [Methods] We exposed 20 healthy young adults to six different types of auditory stimuli. The amounts of palmar sweating resulting from the auditory stimuli were compared between groups with (hypersensitive) and without (non-hypersensitive) auditory hypersensitivity. [Results] Although no group × type of stimulus × first stimulus interaction was observed for the extent of reaction, significant type of stimulus × first stimulus interaction was noted for the extent of reaction. For an 80 dB-6,000 Hz stimulus, the trends for palmar sweating differed between the groups. For the first stimulus, the variance became larger in the hypersensitive group than in the non-hypersensitive group. [Conclusion] Subjects who regularly felt excessive reactions to auditory stimuli tended to have excessive sympathetic responses to repeated loud noises compared with subjects who did not feel excessive reactions. People with auditory hypersensitivity may be classified into several subtypes depending on their reaction patterns to auditory stimuli. PMID:25140103

  19. Steady state decoupling and design of linear multivariable systems

    NASA Technical Reports Server (NTRS)

    Huang, J. Y.; Thaler, G. J.

    1974-01-01

    A constructive criterion for decoupling the steady states of linear multivariable systems is developed. The criterion consists of n(n-1) inequalities with the type numbers of the compensator transfer functions as the unknowns. These unknowns can be chosen to satisfy the inequalities and hence achieve a steady state decoupling scheme. It turns out that pure integrators in the loops play an important role. An extended root locus design method is then developed to take care of the stability and transient response. The overall procedure is applied to the compensation design for STOL C-8A aircraft in the approach mode.

  20. Relationships of body mass index with serum carotenoids, tocopherols and retinol at steady-state and in response to a carotenoid-rich vegetable diet intervention in Filipino schoolchildren.

    PubMed

    Ribaya-Mercado, Judy D; Maramag, Cherry C; Tengco, Lorena W; Blumberg, Jeffrey B; Solon, Florentino S

    2008-04-01

    In marginally nourished children, information is scarce regarding the circulating concentrations of carotenoids and tocopherols, and physiological factors influencing their circulating levels. We determined the serum concentrations of carotenoids, tocopherols and retinol at steady state and in response to a 9-week vegetable diet intervention in 9-12-year-old girls (n=54) and boys (n=65) in rural Philippines. We determined cross-sectional relationships of BMI (body mass index) with serum micronutrient levels, and whether BMI is a determinant of serum carotenoid responses to the ingestion of carotenoid-rich vegetables. We measured dietary nutrient intakes and assessed inflammation by measurement of serum C-reactive protein levels. The children had low serum concentrations of carotenoids, tocopherols and retinol as compared with published values for similar-aged children in the U.S.A. The low serum retinol levels can be ascribed to inadequate diets and were not the result of confounding due to inflammation. Significant inverse correlations of BMI and serum all-trans-beta-carotene, 13-cis-beta-carotene, alpha-carotene, lutein, zeaxanthin and alpha-tocopherol (but not beta-cryptoxanthin, lycopene and retinol) were observed among girls at baseline. The dietary intervention markedly enhanced the serum concentrations of all carotenoids. Changes in serum all-trans-beta-carotene and alpha-carotene (but not changes in lutein, zeaxanthin and beta-cryptoxanthin) in response to the dietary intervention were inversely associated with BMI in girls and boys. Thus, in Filipino school-aged children, BMI is inversely related to the steady-state serum concentrations of certain carotenoids and vitamin E, but not vitamin A, and is a determinant of serum beta- and alpha-carotene responses, but not xanthophyll responses, to the ingestion of carotenoid-rich vegetable meals. PMID:18384277

  1. Frequency-specific disruptions of neuronal oscillations reveal aberrant auditory processing in schizophrenia.

    PubMed

    Hayrynen, Lauren K; Hamm, Jordan P; Sponheim, Scott R; Clementz, Brett A

    2016-06-01

    Individuals with schizophrenia exhibit abnormalities in evoked brain responses in oddball paradigms. These could result from (a) insufficient salience-related cortical signaling (P300), (b) insufficient suppression of irrelevant aspects of the auditory environment, or (c) excessive neural noise. We tested whether disruption of ongoing auditory steady-state responses at predetermined frequencies informed which of these issues contribute to auditory stimulus relevance processing abnormalities in schizophrenia. Magnetoencephalography data were collected for 15 schizophrenia and 15 healthy subjects during an auditory oddball paradigm (25% targets; 1-s interstimulus interval). Auditory stimuli (pure tones: 1 kHz standards, 2 kHz targets) were administered during four continuous background (auditory steady-state) stimulation conditions: (1) no stimulation, (2) 24 Hz, (3) 40 Hz, and (4) 88 Hz. The modulation of the auditory steady-state response (aSSR) and the evoked responses to the transient stimuli were quantified and compared across groups. In comparison to healthy participants, the schizophrenia group showed greater disruption of the ongoing aSSR by targets regardless of steady-state frequency, and reduced amplitude of both M100 and M300 event-related field components. During the no-stimulation condition, schizophrenia patients showed accentuation of left hemisphere 40 Hz response to both standard and target stimuli, indicating an effort to enhance local stimulus processing. Together, these findings suggest abnormalities in auditory stimulus relevance processing in schizophrenia patients stem from insufficient amplification of salient stimuli. PMID:26933842

  2. Auditory Cortex Basal Activity Modulates Cochlear Responses in Chinchillas

    PubMed Central

    León, Alex; Elgueda, Diego; Silva, María A.; Hamamé, Carlos M.; Delano, Paul H.

    2012-01-01

    Background The auditory efferent system has unique neuroanatomical pathways that connect the cerebral cortex with sensory receptor cells. Pyramidal neurons located in layers V and VI of the primary auditory cortex constitute descending projections to the thalamus, inferior colliculus, and even directly to the superior olivary complex and to the cochlear nucleus. Efferent pathways are connected to the cochlear receptor by the olivocochlear system, which innervates outer hair cells and auditory nerve fibers. The functional role of the cortico-olivocochlear efferent system remains debated. We hypothesized that auditory cortex basal activity modulates cochlear and auditory-nerve afferent responses through the efferent system. Methodology/Principal Findings Cochlear microphonics (CM), auditory-nerve compound action potentials (CAP) and auditory cortex evoked potentials (ACEP) were recorded in twenty anesthetized chinchillas, before, during and after auditory cortex deactivation by two methods: lidocaine microinjections or cortical cooling with cryoloops. Auditory cortex deactivation induced a transient reduction in ACEP amplitudes in fifteen animals (deactivation experiments) and a permanent reduction in five chinchillas (lesion experiments). We found significant changes in the amplitude of CM in both types of experiments, being the most common effect a CM decrease found in fifteen animals. Concomitantly to CM amplitude changes, we found CAP increases in seven chinchillas and CAP reductions in thirteen animals. Although ACEP amplitudes were completely recovered after ninety minutes in deactivation experiments, only partial recovery was observed in the magnitudes of cochlear responses. Conclusions/Significance These results show that blocking ongoing auditory cortex activity modulates CM and CAP responses, demonstrating that cortico-olivocochlear circuits regulate auditory nerve and cochlear responses through a basal efferent tone. The diversity of the obtained effects

  3. A high-density EEG investigation into steady state binaural beat stimulation.

    PubMed

    Goodin, Peter; Ciorciari, Joseph; Baker, Kate; Carey, Anne-Marie; Carrey, Anne-Marie; Harper, Michelle; Kaufman, Jordy

    2012-01-01

    Binaural beats are an auditory phenomenon that has been suggested to alter physiological and cognitive processes including vigilance and brainwave entrainment. Some personality traits measured by the NEO Five Factor Model have been found to alter entrainment using pulsing light stimuli, but as yet no studies have examined if this occurs using steady state presentation of binaural beats for a relatively short presentation of two minutes. This study aimed to examine if binaural beat stimulation altered vigilance or cortical frequencies and if personality traits were involved. Thirty-one participants were played binaural beat stimuli designed to elicit a response at either the Theta (7 Hz) or Beta (16 Hz) frequency bands while undertaking a zero-back vigilance task. EEG was recorded from a high-density electrode cap. No significant differences were found in vigilance or cortical frequency power during binaural beat stimulation compared to a white noise control period. Furthermore, no significant relationships were detected between the above and the Big Five personality traits. This suggests a short presentation of steady state binaural beats are not sufficient to alter vigilance or entrain cortical frequencies at the two bands examined and that certain personality traits were not more susceptible than others. PMID:22496862

  4. A High-Density EEG Investigation into Steady State Binaural Beat Stimulation

    PubMed Central

    Goodin, Peter; Ciorciari, Joseph; Baker, Kate; Carrey, Anne-Marie; Harper, Michelle; Kaufman, Jordy

    2012-01-01

    Binaural beats are an auditory phenomenon that has been suggested to alter physiological and cognitive processes including vigilance and brainwave entrainment. Some personality traits measured by the NEO Five Factor Model have been found to alter entrainment using pulsing light stimuli, but as yet no studies have examined if this occurs using steady state presentation of binaural beats for a relatively short presentation of two minutes. This study aimed to examine if binaural beat stimulation altered vigilance or cortical frequencies and if personality traits were involved. Thirty-one participants were played binaural beat stimuli designed to elicit a response at either the Theta (7 Hz) or Beta (16 Hz) frequency bands while undertaking a zero-back vigilance task. EEG was recorded from a high-density electrode cap. No significant differences were found in vigilance or cortical frequency power during binaural beat stimulation compared to a white noise control period. Furthermore, no significant relationships were detected between the above and the Big Five personality traits. This suggests a short presentation of steady state binaural beats are not sufficient to alter vigilance or entrain cortical frequencies at the two bands examined and that certain personality traits were not more susceptible than others. PMID:22496862

  5. Visual-induced expectations modulate auditory cortical responses.

    PubMed

    van Wassenhove, Virginie; Grzeczkowski, Lukasz

    2015-01-01

    Active sensing has important consequences on multisensory processing (Schroeder et al., 2010). Here, we asked whether in the absence of saccades, the position of the eyes and the timing of transient color changes of visual stimuli could selectively affect the excitability of auditory cortex by predicting the "where" and the "when" of a sound, respectively. Human participants were recorded with magnetoencephalography (MEG) while maintaining the position of their eyes on the left, right, or center of the screen. Participants counted color changes of the fixation cross while neglecting sounds which could be presented to the left, right, or both ears. First, clear alpha power increases were observed in auditory cortices, consistent with participants' attention directed to visual inputs. Second, color changes elicited robust modulations of auditory cortex responses ("when" prediction) seen as ramping activity, early alpha phase-locked responses, and enhanced high-gamma band responses in the contralateral side of sound presentation. Third, no modulations of auditory evoked or oscillatory activity were found to be specific to eye position. Altogether, our results suggest that visual transience can automatically elicit a prediction of "when" a sound will occur by changing the excitability of auditory cortices irrespective of the attended modality, eye position or spatial congruency of auditory and visual events. To the contrary, auditory cortical responses were not significantly affected by eye position suggesting that "where" predictions may require active sensing or saccadic reset to modulate auditory cortex responses, notably in the absence of spatial orientation to sounds. PMID:25705174

  6. A simplified analytical solution for thermal response of a one-dimensional, steady state transpiration cooling system in radiative and convective environment

    NASA Technical Reports Server (NTRS)

    Kubota, H.

    1976-01-01

    A simplified analytical method for calculation of thermal response within a transpiration-cooled porous heat shield material in an intense radiative-convective heating environment is presented. The essential assumptions of the radiative and convective transfer processes in the heat shield matrix are the two-temperature approximation and the specified radiative-convective heatings of the front surface. Sample calculations for porous silica with CO2 injection are presented for some typical parameters of mass injection rate, porosity, and material thickness. The effect of these parameters on the cooling system is discussed.

  7. The Politics of the Steady State

    ERIC Educational Resources Information Center

    Taylor, Charles

    1978-01-01

    A steady state society has limits pertaining to population size, non-renewable resources, and production which emits heat or substances into soil, water, or the atmosphere. Respecting these limits means renouncing exponential quantitative growth and accepting a universally available consumption standard. (SW)

  8. Steady-state inductive spheromak operation

    DOEpatents

    Janos, A.C.; Jardin, S.C.; Yamada, M.

    1985-02-20

    The inductively formed spheromak configuration (S-1) can be maintained in a highly stable and controlled fashion. The method described eliminates the restriction to pulsed spheromak plasmas or the use of electrodes for steady-state operation, and, therefore, is a reactor-relevant formation and sustainment method.

  9. Steady-state spheromak reactor studies. Revision

    SciTech Connect

    Krakowski, R.A.; Hagenson, R.L.

    1985-01-01

    After summarizing the essential elements of a gun-sustained spheromak, the potential for a steady-state is explored by means of a comprehensive physics/engineering/costing model. A range of cost-optimized reactor design point is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported.

  10. Thermodynamics of Stability of Nonequilibrium Steady States.

    ERIC Educational Resources Information Center

    Rastogi, R. P.; Shabd, Ram

    1983-01-01

    Presented is a concise and critical account of developments in nonequilibrium thermodynamics. The criterion for stability of nonequilibrium steady states is critically examined for consecutive and monomolecular triangular reactions, autocatalytic reactions, auto-inhibited reactions, and the Lotka-Volterra model. (JN)

  11. Steady-state linear optical properties and Kerr nonlinear optical response of a four-level quantum dot with phonon-assisted transition

    NASA Astrophysics Data System (ADS)

    Yan-Chao, She; Ting-Ting, Luo; Wei-Xi, Zhang; Mao-Wu, Ran; Deng-Long, Wang

    2016-01-01

    The linear optical properties and Kerr nonlinear optical response in a four-level loop configuration GaAs/AlGaAs semiconductor quantum dot are analytically studied with the phonon-assisted transition (PAT). It is shown that the changes among a single electromagnetically induced transparency (EIT) window, a double EIT window and the amplification of the probe field in the absorption curves can be controlled by varying the strength of PAT κ. Meanwhile, double switching from the anomalous dispersion regime to the normal dispersion regime can likely be achieved by increasing the Rabi energy of the external optical control field. Furthermore, we demonstrate that the group velocity of the probe field can be practically regulated by varying the PAT and the intensity of the optical control field. In the nonlinear case, it is shown that the large SPM and XPM can be achieved as linear absorption vanishes simultaneously, and the PAT can suppress both third-order self-Kerr and the cross-Kerr nonlinear effect of the QD. Our study is much more practical than its atomic counterpart due to its flexible design and the controllable interference strength, and may provide some new possibilities for technological applications. Project supported by the National Natural Science Foundation of China (Grant No. 61367003), the Scientific Research Fund of Hunan Provincial Education Department, China (Grant No. 12A140), and the Scientific Research Fund of Guizhou Provincial Education Department, China (Grant Nos. KY[2015]384 and KY[2015]446).

  12. Spectrotemporal resolution tradeoff in auditory processing as revealed by human auditory brainstem responses and psychophysical indices.

    PubMed

    Bidelman, Gavin M; Syed Khaja, Ameenuddin

    2014-06-20

    Auditory filter theory dictates a physiological compromise between frequency and temporal resolution of cochlear signal processing. We examined neurophysiological correlates of these spectrotemporal tradeoffs in the human auditory system using auditory evoked brain potentials and psychophysical responses. Temporal resolution was assessed using scalp-recorded auditory brainstem responses (ABRs) elicited by paired clicks. The inter-click interval (ICI) between successive pulses was parameterized from 0.7 to 25 ms to map ABR amplitude recovery as a function of stimulus spacing. Behavioral frequency difference limens (FDLs) and auditory filter selectivity (Q10 of psychophysical tuning curves) were obtained to assess relations between behavioral spectral acuity and electrophysiological estimates of temporal resolvability. Neural responses increased monotonically in amplitude with increasing ICI, ranging from total suppression (0.7 ms) to full recovery (25 ms) with a temporal resolution of ∼3-4 ms. ABR temporal thresholds were correlated with behavioral Q10 (frequency selectivity) but not FDLs (frequency discrimination); no correspondence was observed between Q10 and FDLs. Results suggest that finer frequency selectivity, but not discrimination, is associated with poorer temporal resolution. The inverse relation between ABR recovery and perceptual frequency tuning demonstrates a time-frequency tradeoff between the temporal and spectral resolving power of the human auditory system. PMID:24793771

  13. Intense steady state neutron source. The CNR reactor

    SciTech Connect

    Difilippo, F.C.; Moon, R.M.; Gambill, W.R.; Moon, R.M.; Primm, R.T. III; West, C.D.

    1986-01-01

    The Center for Neutron Research (CNR) has been proposed in response to the needs - neutron flux, spectrum, and experimental facilities - that have been identified through workshops, studies, and discussions by the neutron-scattering, isotope, and materials irradiation research communities. The CNR is a major new experimental facility consisting of a reactor-based steady state neutron source of unprecedented flux, together with extensive facilities and instruments for neutron scattering, isotope production, materials irradiation, and other areas of research.

  14. Analysis of steady-state characteristics of bistable laser diodes

    SciTech Connect

    Zhong Lichen; Guo Yili

    1987-05-01

    In this paper we analyze the steady-state characteristics of bistable semiconductor laser diode (BILD). A simple model for optical output of BILD is obtained using nonlinear rate equations for electron and photon densities. This model emphasizes the physical mechanisms and parameters responsible for the bistability, gives the state equation and explains the main features of BILD. Bistability with a very large hysteresis in P/sub 0/-P/sub 4/ characteristics is a distinctive feature of BILD.

  15. IL-21R signaling suppresses IL-17+ gamma delta T cell responses and production of IL-17 related cytokines in the lung at steady state and after Influenza A virus infection.

    PubMed

    Moser, Emily K; Sun, Jie; Kim, Taeg S; Braciale, Thomas J

    2015-01-01

    Influenza A virus (IAV) infection of the respiratory tract elicits a robust immune response, which is required for efficient virus clearance but at the same time can contribute to lung damage and enhanced morbidity. IL-21 is a member of the type I cytokine family and has many different immune-modulatory functions during acute and chronic virus infections, although its role in IAV infection has not been fully evaluated. In this report we evaluated the contributions of IL-21/IL-21 receptor (IL-21R) signaling to host defense in a mouse model of primary IAV infection using IL-21R knock out (KO) mice. We found that lack of IL-21R signaling had no significant impact on virus clearance, adaptive T cell responses, or myeloid cell accumulations in the respiratory tract. However, a subset of inflammatory cytokines were elevated in the bronchoalveolar lavage fluid of IL-21R KO mice, including IL-17. Although there was only a small increase in Th17 cells in the lungs of IL-21R KO mice, we observed a dramatic increase in gamma delta (γδ) T cells capable of producing IL-17 both after IAV infection and at steady state in the respiratory tract. Finally, we found that IL-21R signaling suppressed the accumulation of IL-17+ γδ T cells in the respiratory tract intrinsically. Thus, our study reveals a previously unrecognized role of IL-21R signaling in regulating IL-17 production by γδ T cells. PMID:25849970

  16. Steady- and non-steady-state carbonate-silicate controls on atmospheric CO2

    USGS Publications Warehouse

    Sundquist, E.T.

    1991-01-01

    Two contrasting hypotheses have recently been proposed for the past long-term relation between atmospheric CO2 and the carbonate-silicate geochemical cycle. One approach (Berner, 1990) suggests that CO2 levels have varied in a manner that has maintained chemical weathering and carbonate sedimentation at a steady state with respect to tectonically controlled decarbonation reactions. A second approach (Raymo et al., 1988), applied specificlly to the late Cenozoic, suggests a decrease in CO2 caused by an uplift-induced increase in chemical weathering, without regard to the rate of decarbonation. According to the steady-state (first) hypothesis, increased weathering and carbonate sedimentation are generally associated with increasing atmospheric CO2, whereas the uplift (second) hypothesis implies decreasing CO2 under the same conditions. An ocean-atmosphere-sediment model has been used to assess the response of atmospheric CO2 and carbonate sedimentation to global perturbations in chemical weathering and decarbonation reactions. Although this assessment is theoretical and cannot yet be related to the geologic record, the model simulations compare steady-state and non-steady-state carbonate-silicate cycle response. The e-fold response time of the 'CO2-weathering' feedback mechanism is between 300 and 400 ka. The response of carbonate sedimentation is much more rapid. These response times provide a measure of the strength of steady-state assumptions, and imply that certain systematic relations are sustained throughout steady-state and non-steady-state scenarios for the carbonate-silicate cycle. The simulations suggest that feedbacks can maintain the system near a steady state, but that non-steady-state effects may contribute to long-term trends. The steady-state and uplift hypotheses are not necessarily incompatible over time scales of a few million years. ?? 1991.

  17. Steady state compact toroidal plasma production

    DOEpatents

    Turner, William C.

    1986-01-01

    Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.

  18. Fractionated Reaction Time Responses to Auditory and Electrocutaneous Stimuli.

    ERIC Educational Resources Information Center

    Beehler, Pamela J. Hoyes; Kamen, Gary

    1986-01-01

    An investigation was conducted to equate auditory and electrocutaneous stimuli. These equated stimuli were used in a second investigation examining neuromotor responses to stimuli of varying intensity. Results are provided. (Author/MT)

  19. Analysis of slow transitions between nonequilibrium steady states

    NASA Astrophysics Data System (ADS)

    Mandal, Dibyendu; Jarzynski, Christopher

    2016-06-01

    Transitions between nonequilibrium steady states obey a generalized Clausius inequality, which becomes an equality in the quasistatic limit. For slow but finite transitions, we show that the behavior of the system is described by a response matrix whose elements are given by a far-from-equilibrium Green–Kubo formula, involving the decay of correlations evaluated in the nonequilibrium steady state. This result leads to a fluctuation-dissipation relation between the mean and variance of the nonadiabatic entropy production, Δ {{s}\\text{na}} . Furthermore, our results extend—to nonequilibrium steady states—the thermodynamic metric structure introduced by Sivak and Crooks for analyzing minimal-dissipation protocols for transitions between equilibrium states.

  20. Theory of Steady-State Superradiance

    NASA Astrophysics Data System (ADS)

    Xu, Minghui

    In this thesis, I describe the theoretical development of the superradiant laser, or laser in the extreme bad-cavity regime. In this regime, the cavity decay rate is much greater than the atomic dynamics. The atoms emit photons into the cavity mode superradiantly in steady state. We develop group-theoretic methods that enable us to exactly solve mesoscopic systems with hundreds of atoms. We demonstrate the synchronization of atomic dipoles in steady-state superradiance. With this synchronized system, we propose conditional Ramsey spectroscopy which allows us to observe Ramsey fringes indefinitely, even in the presence of atomic decoherence. Furthermore, we explore manifestations of synchronization in the quantum realm with two superradiant atomic ensembles. We show that two such ensembles exhibit a dynamical phase transition from two disparate oscillators to quantum phase-locked dynamics. Finally, we study the mechanical eect of the light-atom interaction in the steady-state superradiance. We find efficient many-body cooling of atoms. The work described in this thesis lays the theoretical foundation for the superradiant laser and for a potential future of active optical frequency standards.

  1. Primary auditory cortical responses to electrical stimulation of the thalamus.

    PubMed

    Atencio, Craig A; Shih, Jonathan Y; Schreiner, Christoph E; Cheung, Steven W

    2014-03-01

    Cochlear implant electrical stimulation of the auditory system to rehabilitate deafness has been remarkably successful. Its deployment requires both an intact auditory nerve and a suitably patent cochlear lumen. When disease renders prerequisite conditions impassable, such as in neurofibromatosis type II and cochlear obliterans, alternative treatment targets are considered. Electrical stimulation of the cochlear nucleus and midbrain in humans has delivered encouraging clinical outcomes, buttressing the promise of central auditory prostheses to mitigate deafness in those who are not candidates for cochlear implantation. In this study we explored another possible implant target: the auditory thalamus. In anesthetized cats, we first presented pure tones to determine frequency preferences of thalamic and cortical sites. We then electrically stimulated tonotopically organized thalamic sites while recording from primary auditory cortical sites using a multichannel recording probe. Cathode-leading biphasic thalamic stimulation thresholds that evoked cortical responses were much lower than published accounts of cochlear and midbrain stimulation. Cortical activation dynamic ranges were similar to those reported for cochlear stimulation, but they were narrower than those found through midbrain stimulation. Our results imply that thalamic stimulation can activate auditory cortex at low electrical current levels and suggest an auditory thalamic implant may be a viable central auditory prosthesis. PMID:24335216

  2. Clinical applications of the human brainstem responses to auditory stimuli

    NASA Technical Reports Server (NTRS)

    Galambos, R.; Hecox, K.

    1975-01-01

    A technique utilizing the frequency following response (FFR) (obtained by auditory stimulation, whereby the stimulus frequency and duration are mirror-imaged in the resulting brainwaves) as a clinical tool for hearing disorders in humans of all ages is presented. Various medical studies are discussed to support the clinical value of the technique. The discovery and origin of the FFR and another significant brainstem auditory response involved in studying the eighth nerve is also discussed.

  3. The steady-state phase distribution of the motor switch complex model of Halobacterium salinarum.

    PubMed

    del Rosario, Ricardo C H; Diener, Francine; Diener, Marc; Oesterhelt, Dieter

    2009-12-01

    Steady-state analysis is performed on the kinetic model for the switch complex of the flagellar motor of Halobacterium salinarum (Nutsch et al.). The existence and uniqueness of a positive steady-state of the system is established and it is demonstrated why the steady-state is centered around the competent phase, a state of the motor in which it is able to respond to light stimuli. It is also demonstrated why the steady-state shifts to the refractory phase when the steady-state value of the response regulator CheYP increases. This work is one aspect of modeling in systems biology wherein the mathematical properties of a model are established. PMID:19857501

  4. Auditory brainstem response to complex sounds: a tutorial

    PubMed Central

    Skoe, Erika; Kraus, Nina

    2010-01-01

    This tutorial provides a comprehensive overview of the methodological approach to collecting and analyzing auditory brainstem responses to complex sounds (cABRs). cABRs provide a window into how behaviorally relevant sounds such as speech and music are processed in the brain. Because temporal and spectral characteristics of sounds are preserved in this subcortical response, cABRs can be used to assess specific impairments and enhancements in auditory processing. Notably, subcortical function is neither passive nor hardwired but dynamically interacts with higher-level cognitive processes to refine how sounds are transcribed into neural code. This experience-dependent plasticity, which can occur on a number of time scales (e.g., life-long experience with speech or music, short-term auditory training, online auditory processing), helps shape sensory perception. Thus, by being an objective and non-invasive means for examining cognitive function and experience-dependent processes in sensory activity, cABRs have considerable utility in the study of populations where auditory function is of interest (e.g., auditory experts such as musicians, persons with hearing loss, auditory processing and language disorders). This tutorial is intended for clinicians and researchers seeking to integrate cABRs into their clinical and/or research programs. PMID:20084007

  5. Visual-induced expectations modulate auditory cortical responses

    PubMed Central

    van Wassenhove, Virginie; Grzeczkowski, Lukasz

    2015-01-01

    Active sensing has important consequences on multisensory processing (Schroeder et al., 2010). Here, we asked whether in the absence of saccades, the position of the eyes and the timing of transient color changes of visual stimuli could selectively affect the excitability of auditory cortex by predicting the “where” and the “when” of a sound, respectively. Human participants were recorded with magnetoencephalography (MEG) while maintaining the position of their eyes on the left, right, or center of the screen. Participants counted color changes of the fixation cross while neglecting sounds which could be presented to the left, right, or both ears. First, clear alpha power increases were observed in auditory cortices, consistent with participants' attention directed to visual inputs. Second, color changes elicited robust modulations of auditory cortex responses (“when” prediction) seen as ramping activity, early alpha phase-locked responses, and enhanced high-gamma band responses in the contralateral side of sound presentation. Third, no modulations of auditory evoked or oscillatory activity were found to be specific to eye position. Altogether, our results suggest that visual transience can automatically elicit a prediction of “when” a sound will occur by changing the excitability of auditory cortices irrespective of the attended modality, eye position or spatial congruency of auditory and visual events. To the contrary, auditory cortical responses were not significantly affected by eye position suggesting that “where” predictions may require active sensing or saccadic reset to modulate auditory cortex responses, notably in the absence of spatial orientation to sounds. PMID:25705174

  6. Siple Dome: Is it in Steady State?

    NASA Astrophysics Data System (ADS)

    Pettit, E. C.; Waddington, E. D.; Nereson, N. A.; Zumberge, M. A.; Hamilton, G. S.

    2001-12-01

    Changes in the West Antarctic Ice Sheet since the end of the last ice age have implications for how we interpret its present behavior, in terms of both its stability and its record of climate history. Siple Dome, the ridge between Ice Streams C and D, is not presently thinning and is close to being in balance with present environmental conditions. We present three independent measurements of ice thickness change in the divide region of Siple Dome: a GPS surface horizontal strain network, fiber optic vertical strain measurements at depth, and precision GPS measurements of vertical motion of near-surface ice ("coffee-can" method). From the horizontal strain network, we calculate the divergence of the horizontal velocity. This divergence is equal to the gradient of vertical velocity at the surface and, with some assumptions about the distribution of strain rates with depth, we can calculate the vertical velocity at the surface. For steady state, the vertical velocity must be balanced by the local accumulation rate. The fiber optic instruments provide a profile of the relative vertical velocity with depth. We fit a theoretical vertical velocity pattern to these data and extrapolate to find the surface vertical velocity. Our third method (coffee-can) directly measures the vertical motion of a marker 20 meters deep using precision GPS and compares it with the local long-term rate of snow accumulation to calculate the net rate of ice sheet thickness change. All three methods reach the same conclusion: Siple Dome is currently very close to being in steady state. This result has two implications. First, ice dynamics models developed to interpret radar images or ice core data can assume steady state behavior, simplifying the models. Second, our result suggests that the central part of the Ross Embayment may have had a low-elevation profile during the late Holocene, even though other areas of the WAIS may have been thicker.

  7. Intensity fluctuations in steady-state superradiance

    SciTech Connect

    Meiser, D.; Holland, M. J.

    2010-06-15

    Alkaline-earth-metal-like atoms with ultranarrow optical transitions enable superradiance in steady state. The emitted light promises to have an unprecedented stability with a linewidth as narrow as a few millihertz. In order to evaluate the potential usefulness of this light source as an ultrastable oscillator in clock and precision metrology applications, it is crucial to understand the noise properties of this device. In this paper, we present a detailed analysis of the intensity fluctuations by means of Monte Carlo simulations and semiclassical approximations. We find that the light exhibits bunching below threshold, is to a good approximation coherent in the superradiant regime, and is chaotic above the second threshold.

  8. Intense steady state electron beam generator

    DOEpatents

    Hershcovitch, Ady; Kovarik, Vincent J.; Prelec, Krsto

    1990-01-01

    An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source.

  9. Intense steady state electron beam generator

    DOEpatents

    Hershcovitch, A.; Kovarik, V.J.; Prelec, K.

    1990-07-17

    An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source. 2 figs.

  10. Occipital γ response to auditory stimulation in patients with schizophrenia.

    PubMed

    Basar-Eroglu, Canan; Mathes, Birgit; Brand, Andreas; Schmiedt-Fehr, Christina

    2011-01-01

    This study investigated changes in gamma oscillations during auditory sensory processing (auditory-evoked gamma responses, AEGR) and target detection (auditory event-related gamma responses, AERGR) in healthy controls (n=10) and patients with schizophrenia (n=10) using both single-trial and averaged time-frequency data analysis. The results show that single-trial gamma responses in patients were altered in magnitude and topographic pattern for both the AEGR and the AERGR experimental conditions, whereas no differences were found for the averaged evoked gamma response. At the single-trial level, auditory stimuli elicited higher gamma responses at both anterior and occipital sites in patients with schizophrenia compared to controls. Furthermore, in patients with schizophrenia target detection compared to passive listening to stimuli was related to increased single-trial gamma power at frontal sites. In controls enhancement of the gamma response was only apparent for the averaged gamma response, with a distribution largely restricted to anterior sites. The differences in oscillatory activity between healthy controls and patients with schizophrenia were not reflected in the behavioral measure (i.e., counting targets). We conclude that gamma activity triggered by auditory stimuli in schizophrenic patients might have less selectivity in timing and alterations in topography and may show changes in amplitude modulation with task demands. The present study may indicate that in patients with schizophrenia neuronal information is not adequately transferred, possibly due to an over-excitability of neuronal networks and excessive pruning of local connections in association cortex. PMID:21056599

  11. Auditory Evoked Responses in Neonates by MEG

    SciTech Connect

    Hernandez-Pavon, J. C.; Sosa, M.; Lutter, W. J.; Maier, M.; Wakai, R. T.

    2008-08-11

    Magnetoencephalography is a biomagnetic technique with outstanding potential for neurodevelopmental studies. In this work, we have used MEG to determinate if newborns can discriminate between different stimuli during the first few months of life. Five neonates were stimulated during several minutes with auditory stimulation. The results suggest that the newborns are able to discriminate between different stimuli despite their early age.

  12. Steady State Growth of Continental Crust?

    NASA Astrophysics Data System (ADS)

    Bowring, S. A.; Bauer, A.; Dudas, F. O.; Schoene, B.; McLean, N. M.

    2012-12-01

    any age. If one accepts that the probability of preserving old crust decreases with increasing age, the few exposures of rocks older than 3.5 Ga should not be surprising. The thickness and compositional differences between Archean and younger lithospheric mantle are not fully understood nor is the role of thicker buoyant mantle in preserving continental crust; these lead to the question of whether the preserved rock record is representative of what formed. It is notable that the oldest known rocks, the ca. 4.0 Ga Acasta Gneisses, are tonalities-granodiorites-granites with evidence for the involvement of even older crust and that the oldest detrital zircons from Australia (ca. 4.0-4.4 Ga) are thought to have been derived from granitoid sources. The global Hf and Nd isotope databases are compatible with both depleted and enriched sources being present from at least 4.0 Ga to the present and that the lack of evolution of the MORB source or depleted mantle is due to recycling of continental crust throughout earth history. Using examples from the Slave Province and southern Africa, we argue that Armstrong's concept of steady state crustal growth and recycling via plate tectonics still best explains the modern geological and geochemical data.

  13. Steady state phreatic surfaces in sloping aquifers

    NASA Astrophysics Data System (ADS)

    LoáIciga, Hugo A.

    2005-08-01

    Steady state groundwater flow driven by constant recharge in an unconfined aquifer overlying sloping bedrock is shown to be represented, using the Dupuit approximation, by an ordinary differential equation of the Abel type y(x) · y'(x) + a · y(x) + x = 0, whose analytical solution is derived in this work. This article first investigates the case of zero saturated thickness at the upstream boundary, a flow system reminiscent of perched groundwater created by percolation of precipitation or irrigation in a sloping aquifer fully draining at its downstream boundary. A variant of this flow system occurs when the phreatic surface mounds and produces groundwater discharge toward the upstream boundary. This variant is a generalization of the classical groundwater flow problem involving two lakes connected by an aquifer, the latter being on sloping terrain in this instance. Analytical solutions for the phreatic surface's steady state geometry are derived for the case of monotonically declining hydraulic head as well as for the case of a mounded phreatic surface. These solutions are of practical interest in drainage studies, slope stability, and runoff formation investigations. It is shown that the flow factor a = -? tan β (where K, N, and tan β are the hydraulic conductivity, vertical recharge, and aquifer slope, respectively) has a commanding role on the phreatic surface's solutions. Two computational examples illustrate the implementation of this article's results.

  14. Steady state phreatic surfaces in sloping aquifers

    NASA Astrophysics Data System (ADS)

    Loáiciga, Hugo A.

    2005-08-01

    Steady state groundwater flow driven by constant recharge in an unconfined aquifer overlying sloping bedrock is shown to be represented, using the Dupuit approximation, by an ordinary differential equation of the Abel type y(x) . y'(x) + a . y(x) + x = 0, whose analytical solution is derived in this work. This article first investigates the case of zero saturated thickness at the upstream boundary, a flow system reminiscent of perched groundwater created by percolation of precipitation or irrigation in a sloping aquifer fully draining at its downstream boundary. A variant of this flow system occurs when the phreatic surface mounds and produces groundwater discharge toward the upstream boundary. This variant is a generalization of the classical groundwater flow problem involving two lakes connected by an aquifer, the latter being on sloping terrain in this instance. Analytical solutions for the phreatic surface's steady state geometry are derived for the case of monotonically declining hydraulic head as well as for the case of a mounded phreatic surface. These solutions are of practical interest in drainage studies, slope stability, and runoff formation investigations. It is shown that the flow factor a = -$\\sqrt{{\\rm K}/{\\rm N} tan β (where K, N, and tan β are the hydraulic conductivity, vertical recharge, and aquifer slope, respectively) has a commanding role on the phreatic surface's solutions. Two computational examples illustrate the implementation of this article's results.

  15. STEADY-STATE SOLUTIONS TO PBPK MODELS AND THEIR APPLICATIONS TO RISK ASSESSMENT I: ROUTE-TO-ROUTE EXTRAPOLATION OF VOLATILE CHEMICALS - AUTHORS' RESPONSE TO LETTER BY DR. KENNETH BOGEN

    EPA Science Inventory

    Dear Editor: We are disappointed that Dr. Bogen felt our paper(1) “adds little new” to previously published work utilizing steady state solutions to PBPK models. Moreover, it was not our intention to be either “dismissive” or “misleading” in our admittedly brief citation of the...

  16. An Intuitive Approach to Steady-State Kinetics.

    ERIC Educational Resources Information Center

    Raines, Ronald T.; Hansen, David E.

    1988-01-01

    Attempts to provide an intuitive understanding of steady state kinetics. Discusses the meaning of steady state and uses free energy profiles to illustrate and follow complex kinetic and thermodynamic relationships. Provides examples with explanations. (MVL)

  17. An auditory-periphery model of the effects of acoustic trauma on auditory nerve responses

    NASA Astrophysics Data System (ADS)

    Bruce, Ian C.; Sachs, Murray B.; Young, Eric D.

    2003-01-01

    Acoustic trauma degrades the auditory nerve's tonotopic representation of acoustic stimuli. Recent physiological studies have quantified the degradation in responses to the vowel eh and have investigated amplification schemes designed to restore a more correct tonotopic representation than is achieved with conventional hearing aids. However, it is difficult from the data to quantify how much different aspects of the cochlear pathology contribute to the impaired responses. Furthermore, extensive experimental testing of potential hearing aids is infeasible. Here, both of these concerns are addressed by developing models of the normal and impaired auditory peripheries that are tested against a wide range of physiological data. The effects of both outer and inner hair cell status on model predictions of the vowel data were investigated. The modeling results indicate that impairment of both outer and inner hair cells contribute to degradation in the tonotopic representation of the formant frequencies in the auditory nerve. Additionally, the model is able to predict the effects of frequency-shaping amplification on auditory nerve responses, indicating the model's potential suitability for more rapid development and testing of hearing aid schemes.

  18. Electrical Brain Responses to an Auditory Illusion and the Impact of Musical Expertise

    PubMed Central

    Ioannou, Christos I.; Pereda, Ernesto; Lindsen, Job P.; Bhattacharya, Joydeep

    2015-01-01

    The presentation of two sinusoidal tones, one to each ear, with a slight frequency mismatch yields an auditory illusion of a beating frequency equal to the frequency difference between the two tones; this is known as binaural beat (BB). The effect of brief BB stimulation on scalp EEG is not conclusively demonstrated. Further, no studies have examined the impact of musical training associated with BB stimulation, yet musicians' brains are often associated with enhanced auditory processing. In this study, we analysed EEG brain responses from two groups, musicians and non-musicians, when stimulated by short presentation (1 min) of binaural beats with beat frequency varying from 1 Hz to 48 Hz. We focused our analysis on alpha and gamma band EEG signals, and they were analysed in terms of spectral power, and functional connectivity as measured by two phase synchrony based measures, phase locking value and phase lag index. Finally, these measures were used to characterize the degree of centrality, segregation and integration of the functional brain network. We found that beat frequencies belonging to alpha band produced the most significant steady-state responses across groups. Further, processing of low frequency (delta, theta, alpha) binaural beats had significant impact on cortical network patterns in the alpha band oscillations. Altogether these results provide a neurophysiological account of cortical responses to BB stimulation at varying frequencies, and demonstrate a modulation of cortico-cortical connectivity in musicians' brains, and further suggest a kind of neuronal entrainment of a linear and nonlinear relationship to the beating frequencies. PMID:26065708

  19. Short-term enhancement and suppression of dolphin auditory evoked responses following echolocation click emission.

    PubMed

    Finneran, James J; Echon, Roxanne; Mulsow, Jason; Houser, Dorian S

    2016-07-01

    Biosonar gain control mechanisms in a bottlenose dolphin were investigated by measuring the auditory steady-state response (ASSR) to an external tone while the animal echolocated. The dolphin performed an echo change-detection task that utilized electronically synthesized echoes with echo delays corresponding to 25- and 50-m target range. During the task, amplitude modulated tones with carrier frequencies from 25 to 125 kHz were continuously presented and the instantaneous electroencephalogram stored for later analysis. ASSRs were extracted from the electroencephalogram by synchronously averaging time epochs temporally aligned with the onset of the external tone modulation cycle nearest to each of the dolphin's echolocation clicks. Results showed an overall suppression of the ASSR amplitude for tones with frequencies near the click center frequencies. A larger, temporary suppression of the ASSR amplitude was also measured at frequencies above 40-50 kHz, while a temporary enhancement was observed at lower frequencies. Temporal patterns for ASSR enhancement or suppression were frequency-, level-, and range-dependent, with recovery to pre-click values occurring within the two-way travel time. Suppressive effects fit the patterns expected from forward masking by the emitted biosonar pulse, while the specific mechanisms responsible for the frequency-dependent enhancement are unknown. PMID:27475154

  20. Auditory Evoked Potential Response and Hearing Loss: A Review

    PubMed Central

    Paulraj, M. P; Subramaniam, Kamalraj; Yaccob, Sazali Bin; Adom, Abdul H. Bin; Hema, C. R

    2015-01-01

    Hypoacusis is the most prevalent sensory disability in the world and consequently, it can lead to impede speech in human beings. One best approach to tackle this issue is to conduct early and effective hearing screening test using Electroencephalogram (EEG). EEG based hearing threshold level determination is most suitable for persons who lack verbal communication and behavioral response to sound stimulation. Auditory evoked potential (AEP) is a type of EEG signal emanated from the brain scalp by an acoustical stimulus. The goal of this review is to assess the current state of knowledge in estimating the hearing threshold levels based on AEP response. AEP response reflects the auditory ability level of an individual. An intelligent hearing perception level system enables to examine and determine the functional integrity of the auditory system. Systematic evaluation of EEG based hearing perception level system predicting the hearing loss in newborns, infants and multiple handicaps will be a priority of interest for future research. PMID:25893012

  1. Auditory Brainstem Responses in Young Adults with Down Syndrome.

    ERIC Educational Resources Information Center

    Widen, Judith E.; And Others

    1987-01-01

    In a study of 15 individuals (ages 15-21) with Down Syndrome, auditory brainstem response (ABR) detection levels were elevated, response amplitude reduced, and latency-intensity functions were significantly steeper than for a matched control group. Findings were associated with an impairment in hearing sensitivity at 8000 Hz for the experimental…

  2. High power steady state MPD thrusters

    NASA Astrophysics Data System (ADS)

    Auweter-Kurtz, Monika; Habiger, Harald; Kurtz, Helmut; Schrade, Herbert; Sleziona, Cristian

    1993-04-01

    At the Institut fuer Raumfahrtsysteme (IRS) rotation symmetric magnetoplasmadynamic thrusters with self induced magnetic fields are investigated at high current levels in a steady state operation mode. MPD thrusters with different geometrics were compared, and the influence of mass flow rate and power input on the operating conditions of the thrusters explored. By optical and probe measurements, a systematic investigation of the plasma plume has been started. The investigation of the various instabilities of the arc and the plasma flow appearing at high power levels was continued. The computer code development for the geometry optimization of continuous self-field MPD thrusters, running with argon, was modified by considering higher degrees of ionization, which showed better agreement with the experiment.

  3. Auditory brainstem responses (ABR) in children with neurological disorders.

    PubMed

    el Khateeb, I; Abdul Razzak, B; Moosa, A

    1988-01-01

    Auditory brainstem responses (ABR) were studied in 35 children with neurological disorders and 24 controls. Abnormal results were obtained in 16 patients. All 5 of the patients with metachromatic leukodystrophy had evidence of peripheral and/or central delay in transmission in keeping with evidence of demyelination of both peripheral (i.e. auditory nerve) and central (i.e. brainstem) pathways as occurs in this disorder. Two children with lead poisoning had delayed conduction in the peripheral pathways only and in these there was good correlation between the degree of delay and the ulnar nerve conduction velocity; both improved after chelation therapy. One infant with lead poisoning had central delay only. One infant with osteopetrosis manifested progressive damage to the auditory nerves. Delayed conduction was also found in one patient each with hydrocephalus, spinal muscular atrophy, and in 2 infants with cerebral palsy. No responses were obtained in one infant with congenital rubella, one deaf-mute and one child with an undiagnosed degenerative neurological disease. Auditory brainstem responses are of value in detecting disturbances of the auditory nerve or brainstem in children with various neurological disorders. PMID:3218703

  4. Seeing the Song: Left Auditory Structures May Track Auditory-Visual Dynamic Alignment

    PubMed Central

    Mossbridge, Julia A.; Grabowecky, Marcia; Suzuki, Satoru

    2013-01-01

    Auditory and visual signals generated by a single source tend to be temporally correlated, such as the synchronous sounds of footsteps and the limb movements of a walker. Continuous tracking and comparison of the dynamics of auditory-visual streams is thus useful for the perceptual binding of information arising from a common source. Although language-related mechanisms have been implicated in the tracking of speech-related auditory-visual signals (e.g., speech sounds and lip movements), it is not well known what sensory mechanisms generally track ongoing auditory-visual synchrony for non-speech signals in a complex auditory-visual environment. To begin to address this question, we used music and visual displays that varied in the dynamics of multiple features (e.g., auditory loudness and pitch; visual luminance, color, size, motion, and organization) across multiple time scales. Auditory activity (monitored using auditory steady-state responses, ASSR) was selectively reduced in the left hemisphere when the music and dynamic visual displays were temporally misaligned. Importantly, ASSR was not affected when attentional engagement with the music was reduced, or when visual displays presented dynamics clearly dissimilar to the music. These results appear to suggest that left-lateralized auditory mechanisms are sensitive to auditory-visual temporal alignment, but perhaps only when the dynamics of auditory and visual streams are similar. These mechanisms may contribute to correct auditory-visual binding in a busy sensory environment. PMID:24194873

  5. Seeing the song: left auditory structures may track auditory-visual dynamic alignment.

    PubMed

    Mossbridge, Julia A; Grabowecky, Marcia; Suzuki, Satoru

    2013-01-01

    Auditory and visual signals generated by a single source tend to be temporally correlated, such as the synchronous sounds of footsteps and the limb movements of a walker. Continuous tracking and comparison of the dynamics of auditory-visual streams is thus useful for the perceptual binding of information arising from a common source. Although language-related mechanisms have been implicated in the tracking of speech-related auditory-visual signals (e.g., speech sounds and lip movements), it is not well known what sensory mechanisms generally track ongoing auditory-visual synchrony for non-speech signals in a complex auditory-visual environment. To begin to address this question, we used music and visual displays that varied in the dynamics of multiple features (e.g., auditory loudness and pitch; visual luminance, color, size, motion, and organization) across multiple time scales. Auditory activity (monitored using auditory steady-state responses, ASSR) was selectively reduced in the left hemisphere when the music and dynamic visual displays were temporally misaligned. Importantly, ASSR was not affected when attentional engagement with the music was reduced, or when visual displays presented dynamics clearly dissimilar to the music. These results appear to suggest that left-lateralized auditory mechanisms are sensitive to auditory-visual temporal alignment, but perhaps only when the dynamics of auditory and visual streams are similar. These mechanisms may contribute to correct auditory-visual binding in a busy sensory environment. PMID:24194873

  6. Modeling of Auditory Neuron Response Thresholds with Cochlear Implants.

    PubMed

    Venail, Frederic; Mura, Thibault; Akkari, Mohamed; Mathiolon, Caroline; Menjot de Champfleur, Sophie; Piron, Jean Pierre; Sicard, Marielle; Sterkers-Artieres, Françoise; Mondain, Michel; Uziel, Alain

    2015-01-01

    The quality of the prosthetic-neural interface is a critical point for cochlear implant efficiency. It depends not only on technical and anatomical factors such as electrode position into the cochlea (depth and scalar placement), electrode impedance, and distance between the electrode and the stimulated auditory neurons, but also on the number of functional auditory neurons. The efficiency of electrical stimulation can be assessed by the measurement of e-CAP in cochlear implant users. In the present study, we modeled the activation of auditory neurons in cochlear implant recipients (nucleus device). The electrical response, measured using auto-NRT (neural responses telemetry) algorithm, has been analyzed using multivariate regression with cubic splines in order to take into account the variations of insertion depth of electrodes amongst subjects as well as the other technical and anatomical factors listed above. NRT thresholds depend on the electrode squared impedance (β = -0.11 ± 0.02, P < 0.01), the scalar placement of the electrodes (β = -8.50 ± 1.97, P < 0.01), and the depth of insertion calculated as the characteristic frequency of auditory neurons (CNF). Distribution of NRT residues according to CNF could provide a proxy of auditory neurons functioning in implanted cochleas. PMID:26236725

  7. Evoked response study tool: a portable, rugged system for single and multiple auditory evoked potential measurements.

    PubMed

    Finneran, James J

    2009-07-01

    Although the potential of using portable auditory evoked potential systems for field testing of stranded cetaceans has been long recognized, commercial systems for evoked potential measurements generally do not possess the bandwidth required for testing odontocete cetaceans and are not suitable for field use. As a result, there have been a number of efforts to develop portable evoked potential systems for field testing of cetaceans. This paper presents another such system, called the evoked response study tool (EVREST). EVREST is a Windows-based hardware/software system designed for calibrating sound stimuli and recording and analyzing transient and steady-state evoked potentials. The EVREST software features a graphical user interface, real-time analysis and visualization of recorded data, a variety of stimulus options, and a high level of automation. The system hardware is portable, rugged, battery-powered, and possesses a bandwidth that encompasses the audible range of echolocating odontocetes, making the system suitable for field testing of stranded or rehabilitating cetaceans. PMID:19603907

  8. A model for simulation of electrically evoked auditory brainstem responses

    NASA Astrophysics Data System (ADS)

    Miller, Douglas A.; Matin, Mohammed A.

    2009-08-01

    An important aspect of research in the continued development of cochlear implants is the in vivo assessment of signal processing algorithms. One technique that has been used is evoked potentials, the recording of neural responses to auditory stimulation. Depending on the latency of the observed response, the evoked potential indicates neural activity at the various neurological structures of the auditory system. Electrically evoked ABRs are commonly measured in hearing-impaired patients who have cochlear implants, via electrical stimulation delivered by electrodes in the implanted array. This research explores the use of MATLAB for the purpose of developing a model for electrically evoked auditory brainstem responses (ABRs). The simulation model developed in this study takes as its input the stimulus current intensity level, and uses function vectors and equations derived from measured ABRs, to generate an approximation of the evoked surface potentials. A function vector is used to represent the combined firing of the neurons of the auditory nervous system that are needed to elicit a measurable response. Equations have been derived to represent the latency and stimulus amplitude scaling functions. The simulation also accounts for other neural activity that can be present in and contaminate an ABR recording, and reduces it through time-locked averaging of the simulated response. In the MATLAB simulation, the model performs well and delivers results that compare favorably with the results measured from the research subjects.

  9. Newborn Auditory Brainstem Evoked Responses (ABRs): Prenatal and Contemporary Correlates.

    ERIC Educational Resources Information Center

    Murray, Ann D.

    1988-01-01

    Presented are a literature review and new data on correlates of newborn auditory brainstem evoked responses (ABRs). Concludes that disorders of the central components of the ABR may be more of prenatal than of postnatal origin. The I-V interval had low but reliable correlations with four of 11 Brazelton scale variables. (RH)

  10. Neonatal Auditory Brainstem Responses Recorded from Four Electrode Montages.

    ERIC Educational Resources Information Center

    Stuart, Andrew; And Others

    1996-01-01

    Simultaneous auditory brainstem responses (ABRs) to click stimuli at 30 and 60 decibels were recorded from 16 full-term neonates with 4 different electrode arrays. Results indicated that ABR waveforms were morphologically similar to those recorded in adults. Waveform expression was variable with different electrode recording montages. (Author/DB)

  11. Auditory Brainstem Evoked Responses in Newborns with Down Syndrome

    ERIC Educational Resources Information Center

    Kittler, Phyllis M.; Phan, Ha T. T.; Gardner, Judith M.; Miroshnichenko, Inna; Gordon, Anne; Karmel, Bernard Z.

    2009-01-01

    Auditory brainstem evoked responses (ABRs) were compared in 15 newborns with Down syndrome and 15 sex-, age-, and weight-matched control newborns. Participants had normal ABRs based upon values specific to 32- to 42-weeks postconceptional age. Although Wave III and Wave V component latencies and the Wave I-III interpeak latency (IPL) were shorter…

  12. Inconsistencies in steady-state thermodynamics

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald; Motai, Ricardo

    2014-03-01

    We address the issue of extending thermodynamics to nonequilibrium steady states. Using driven stochastic lattice gases, we ask whether consistent definitions of an effective chemical potential μ, and an effective temperature Te, are possible. μ and Te are determined via coexistence, i.e., zero flux of particles and energy between the driven system and a reservoir. In the lattice gas with nearest-neighbor exclusion, temperature is not relevant, and we find that the effective chemical potential, a function of density and drive strength, satisfies the zeroth law, and correctly predicts the densities of coexisting systems. In the Katz-Lebowitz-Spohn driven lattice gas both μ and Te need to be defined. We show analytically that in this case the zeroth law is violated for Metropolis exchange rates, and determine the size of the violations numerically. The zeroth law appears to be violated for generic exchange rates. Remarkably, the system-reservoir coupling proposed by Sasa and Tasaki [J. Stat. Phys. 125, 125 (2006), 10.1007/s10955-005-9021-7] is free of inconsistencies, and the zeroth law holds. This is because the rate depends only on the state of the donor system, and is independent of that of the acceptor.

  13. Steady State Vapor Bubble in Pool Boiling.

    PubMed

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  14. Steady State Vapor Bubble in Pool Boiling

    NASA Astrophysics Data System (ADS)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-02-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  15. Maximal lactate steady state in Judo

    PubMed Central

    de Azevedo, Paulo Henrique Silva Marques; Pithon-Curi, Tania; Zagatto, Alessandro Moura; Oliveira, João; Perez, Sérgio

    2014-01-01

    Summary Background: the purpose of this study was to verify the validity of respiratory compensation threshold (RCT) measured during a new single judo specific incremental test (JSIT) for aerobic demand evaluation. Methods: to test the validity of the new test, the JSIT was compared with Maximal Lactate Steady State (MLSS), which is the gold standard procedure for aerobic demand measuring. Eight well-trained male competitive judo players (24.3 ± 7.9 years; height of 169.3 ± 6.7cm; fat mass of 12.7 ± 3.9%) performed a maximal incremental specific test for judo to assess the RCT and performed on 30-minute MLSS test, where both tests were performed mimicking the UchiKomi drills. Results: the intensity at RCT measured on JSIT was not significantly different compared to MLSS (p=0.40). In addition, it was observed high and significant correlation between MLSS and RCT (r=0.90, p=0.002), as well as a high agreement. Conclusions: RCT measured during JSIT is a valid procedure to measure the aerobic demand, respecting the ecological validity of Judo. PMID:25332923

  16. Steady State Vapor Bubble in Pool Boiling

    PubMed Central

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  17. Steady-state flow properties of amorphous materials

    NASA Astrophysics Data System (ADS)

    Jadhao, Vikram; O'Connor, Thomas; Robbins, Mark

    2015-03-01

    Molecular dynamics (MD) simulations are used to investigate the steady-state shear flow curves of a standard glass model: the bidisperse Lennard-Jones system. For a wide range of temperatures in the neighborhood of the glass transition temperature Tg predicted by the mode coupling theory, we compute the steady-state shear stress and viscosity as a function of the shear rate γ ˙. At temperatures near and above Tg, the stress crosses over from linear Newtonian behavior at low rates to power law shear-thinning at high rates. As T decreases below Tg, the stress shows a plateau, becoming nearly rate-independent at low γ ˙. There is a weak increase in stress that is consistent with Eyring theory for activated flow of a solid. We find that when the strain rate is reduced to extremely low values, Newtonian behavior appears once more. Insights gained from these simulations are applied to the computation of flow curves of a well-established boundary lubricant: squalane. In the elastohydrodynamic regime, squalane responds like a glassy solid with an Eyring-like response, but at low rates it has a relatively small Newtonian viscosity. Supported by the Army Research Laboratory under Grant W911NF-12-2-0022.

  18. Mechanisms of steady-state nucleate pool boiling in microgravity.

    PubMed

    Lee, Ho Sung

    2002-10-01

    Research on nucleate pool boiling in microgravity using R-113 as a working fluid was conducted using a five-second drop tower and five space flights at a/g approximately 10(-4). A 19 x 38-mm flat gold film heater was used that allowed cine camera viewing both from the side and the bottom of the heater. It was concluded that for both subcooled and saturated liquids long-term steady-state pool boiling can take place in reduced gravity, but the effectiveness of the boiling heat transfer appears to depend on the heater geometry and on the size and the properties of fluids. Heat transfer is enhanced at lower heat flux levels and the CHF increases as the subcooling increases. It was found that several mechanisms are responsible for the steady-state nucleate pool boiling in the absence of buoyancy. The mechanisms considered here are defined and summarized as bubble removal, bubble coalescence, thermocapillary flow, bubble migration, and latent heat transport. PMID:12446341

  19. Steady state volcanism - Evidence from eruption histories of polygenetic volcanoes

    NASA Technical Reports Server (NTRS)

    Wadge, G.

    1982-01-01

    Cumulative volcano volume curves are presented as evidence for steady-state behavior at certain volcanoes and to develop a model of steady-state volcanism. A minimum criteria of five eruptions over a year was chosen to characterize a steady-state volcano. The subsequent model features a constant head of magmatic pressure from a reservoir supplied from depth, a sawtooth curve produced by the magma arrivals or discharge from the subvolcanic reservoir, large volume eruptions with long repose periods, and conditions of nonsupply of magma. The behavior of Mts. Etna, Nyamuragira, and Kilauea are described and show continuous levels of plasma output resulting in cumulative volume increases. Further discussion is made of steady-state andesitic and dacitic volcanism, long term patterns of the steady state, and magma storage, and the lack of a sufficient number of steady-state volcanoes in the world is taken as evidence that further data is required for a comprehensive model.

  20. Response actions influence the categorization of directions in auditory space.

    PubMed

    Velten, Marcella C C; Bläsing, Bettina E; Hermann, Thomas; Vorwerg, Constanze; Schack, Thomas

    2015-01-01

    Spatial region concepts such as "front," "back," "left," and "right" reflect our typical interaction with space, and the corresponding surrounding regions have different statuses in memory. We examined the representation of spatial directions in the auditory space, specifically in how far natural response actions, such as orientation movements toward a sound source, would affect the categorization of egocentric auditory space. While standing in the middle of a circle with 16 loudspeakers, participants were presented acoustic stimuli coming from the loudspeakers in randomized order, and verbally described their directions by using the concept labels "front," "back," "left," "right," "front-right," "front-left," "back-right," and "back-left." Response actions varied in three blocked conditions: (1) facing front, (2) turning the head and upper body to face the stimulus, and (3) turning the head and upper body plus pointing with the hand and outstretched arm toward the stimulus. In addition to a protocol of the verbal utterances, motion capture and video recording generated a detailed corpus for subsequent analysis of the participants' behavior. Chi-square tests revealed an effect of response condition for directions within the left and right sides. We conclude that movement-based response actions influence the representation of auditory space, especially within the sides' regions. Moreover, the representation of auditory space favors the front and the back regions in terms of resolution, which is possibly related to the physiological characteristics of the human auditory system, as well as to the ecological requirements of action control in the different regions. PMID:26300837

  1. Response actions influence the categorization of directions in auditory space

    PubMed Central

    Velten, Marcella C. C.; Bläsing, Bettina E.; Hermann, Thomas; Vorwerg, Constanze; Schack, Thomas

    2015-01-01

    Spatial region concepts such as “front,” “back,” “left,” and “right” reflect our typical interaction with space, and the corresponding surrounding regions have different statuses in memory. We examined the representation of spatial directions in the auditory space, specifically in how far natural response actions, such as orientation movements toward a sound source, would affect the categorization of egocentric auditory space. While standing in the middle of a circle with 16 loudspeakers, participants were presented acoustic stimuli coming from the loudspeakers in randomized order, and verbally described their directions by using the concept labels “front,” “back,” “left,” “right,” “front-right,” “front-left,” “back-right,” and “back-left.” Response actions varied in three blocked conditions: (1) facing front, (2) turning the head and upper body to face the stimulus, and (3) turning the head and upper body plus pointing with the hand and outstretched arm toward the stimulus. In addition to a protocol of the verbal utterances, motion capture and video recording generated a detailed corpus for subsequent analysis of the participants’ behavior. Chi-square tests revealed an effect of response condition for directions within the left and right sides. We conclude that movement-based response actions influence the representation of auditory space, especially within the sides’ regions. Moreover, the representation of auditory space favors the front and the back regions in terms of resolution, which is possibly related to the physiological characteristics of the human auditory system, as well as to the ecological requirements of action control in the different regions. PMID:26300837

  2. CA_OPPUSST - Cantera OPUS Steady State

    Energy Science and Technology Software Center (ESTSC)

    2005-03-01

    The Cantera Opus Steady State (ca-opusst) applications solves steady reacting flow problems in opposed-flow geometries. It is a 1-0 application that represents axisymmetnc 3-0 physical systems that can be reduced via a similarity transformation to a 1-0 mathematical representation. The code contain solutions of the general dynamic equations for the particle distribution functions using a sectional model to describe the particle distribution function. Operators for particle nucleation, coagulation, condensation (i.e., growth/etching via reactions with themore » gas ambient), internal particle reactions. particle transport due to convection and due to molecular transport, are included in the particle general dynamics equation. Heat transport due to radiation exchange of the environment with particles in local thermal equilibrium to the surrounding gas will be included in the enthalpy conservation equation that is solved for the coupled gas! particle system in an upcoming version of the code due in June 2005. The codes use Cantera , a C++ Cal Tech code, for determination of gas phase species transport, reaction, and thermodynamics physical properties and source terms. The Codes use the Cantera Aerosol Dynamics Simulator (CADS) package, a general library for aerosol modeling, to calculate properties and source terms for the aerosol general dynamics equation, including particle formation from gas phase reactions, particle surface chemistry (growth and oxidation), bulk particle chemistry, particle transport by Brownian diffusion, thermophoresis, and diffusiophoresis, and thermal radiative transport involving particles. Also included are post-processing programs, cajost and cajrof, to extract ascii data from binary output files to produce plots.« less

  3. Auditory brainstem responses in the Eastern Screech Owl: An estimate of auditory thresholds

    NASA Astrophysics Data System (ADS)

    Brittan-Powell, Elizabeth F.; Lohr, Bernard; Hahn, D. Caldwell; Dooling, Robert J.

    2005-07-01

    The auditory brainstem response (ABR), a measure of neural synchrony, was used to estimate auditory sensitivity in the eastern screech owl (Megascops asio). The typical screech owl ABR waveform showed two to three prominent peaks occurring within 5 ms of stimulus onset. As sound pressure levels increased, the ABR peak amplitude increased and latency decreased. With an increasing stimulus presentation rate, ABR peak amplitude decreased and latency increased. Generally, changes in the ABR waveform to stimulus intensity and repetition rate are consistent with the pattern found in several avian families. The ABR audiogram shows that screech owls hear best between 1.5 and 6.4 kHz with the most acute sensitivity between 4-5.7 kHz. The shape of the average screech owl ABR audiogram is similar to the shape of the behaviorally measured audiogram of the barn owl, except at the highest frequencies. Our data also show differences in overall auditory sensitivity between the color morphs of screech owls.

  4. Tactile stimulation and hemispheric asymmetries modulate auditory perception and neural responses in primary auditory cortex.

    PubMed

    Hoefer, M; Tyll, S; Kanowski, M; Brosch, M; Schoenfeld, M A; Heinze, H-J; Noesselt, T

    2013-10-01

    Although multisensory integration has been an important area of recent research, most studies focused on audiovisual integration. Importantly, however, the combination of audition and touch can guide our behavior as effectively which we studied here using psychophysics and functional magnetic resonance imaging (fMRI). We tested whether task-irrelevant tactile stimuli would enhance auditory detection, and whether hemispheric asymmetries would modulate these audiotactile benefits using lateralized sounds. Spatially aligned task-irrelevant tactile stimuli could occur either synchronously or asynchronously with the sounds. Auditory detection was enhanced by non-informative synchronous and asynchronous tactile stimuli, if presented on the left side. Elevated fMRI-signals to left-sided synchronous bimodal stimulation were found in primary auditory cortex (A1). Adjacent regions (planum temporale, PT) expressed enhanced BOLD-responses for synchronous and asynchronous left-sided bimodal conditions. Additional connectivity analyses seeded in right-hemispheric A1 and PT for both bimodal conditions showed enhanced connectivity with right-hemispheric thalamic, somatosensory and multisensory areas that scaled with subjects' performance. Our results indicate that functional asymmetries interact with audiotactile interplay which can be observed for left-lateralized stimulation in the right hemisphere. There, audiotactile interplay recruits a functional network of unisensory cortices, and the strength of these functional network connections is directly related to subjects' perceptual sensitivity. PMID:23664954

  5. Auditory brainstem responses in the Eastern Screech Owl: An estimate of auditory thresholds

    USGS Publications Warehouse

    Brittan-Powell, E.F.; Lohr, B.; Hahn, D.C.; Dooling, R.J.

    2005-01-01

    The auditory brainstem response (ABR), a measure of neural synchrony, was used to estimate auditory sensitivity in the eastern screech owl (Megascops asio). The typical screech owl ABR waveform showed two to three prominent peaks occurring within 5 ms of stimulus onset. As sound pressure levels increased, the ABR peak amplitude increased and latency decreased. With an increasing stimulus presentation rate, ABR peak amplitude decreased and latency increased. Generally, changes in the ABR waveform to stimulus intensity and repetition rate are consistent with the pattern found in several avian families. The ABR audiogram shows that screech owls hear best between 1.5 and 6.4 kHz with the most acute sensitivity between 4?5.7 kHz. The shape of the average screech owl ABR audiogram is similar to the shape of the behaviorally measured audiogram of the barn owl, except at the highest frequencies. Our data also show differences in overall auditory sensitivity between the color morphs of screech owls.

  6. Concurrent brain responses to separate auditory and visual targets.

    PubMed

    Finoia, Paola; Mitchell, Daniel J; Hauk, Olaf; Beste, Christian; Pizzella, Vittorio; Duncan, John

    2015-08-01

    In the attentional blink, a target event (T1) strongly interferes with perception of a second target (T2) presented within a few hundred milliseconds. Concurrently, the brain's electromagnetic response to the second target is suppressed, especially a late negative-positive EEG complex including the traditional P3 wave. An influential theory proposes that conscious perception requires access to a distributed, frontoparietal global workspace, explaining the attentional blink by strong mutual inhibition between concurrent workspace representations. Often, however, the attentional blink is reduced or eliminated for targets in different sensory modalities, suggesting a limit to such global inhibition. Using functional magnetic resonance imaging, we confirm that visual and auditory targets produce similar, distributed patterns of frontoparietal activity. In an attentional blink EEG/MEG design, however, an auditory T1 and visual T2 are identified without mutual interference, with largely preserved electromagnetic responses to T2. The results suggest parallel brain responses to target events in different sensory modalities. PMID:26084914

  7. Concurrent brain responses to separate auditory and visual targets

    PubMed Central

    Mitchell, Daniel J.; Hauk, Olaf; Beste, Christian; Pizzella, Vittorio; Duncan, John

    2015-01-01

    In the attentional blink, a target event (T1) strongly interferes with perception of a second target (T2) presented within a few hundred milliseconds. Concurrently, the brain's electromagnetic response to the second target is suppressed, especially a late negative-positive EEG complex including the traditional P3 wave. An influential theory proposes that conscious perception requires access to a distributed, frontoparietal global workspace, explaining the attentional blink by strong mutual inhibition between concurrent workspace representations. Often, however, the attentional blink is reduced or eliminated for targets in different sensory modalities, suggesting a limit to such global inhibition. Using functional magnetic resonance imaging, we confirm that visual and auditory targets produce similar, distributed patterns of frontoparietal activity. In an attentional blink EEG/MEG design, however, an auditory T1 and visual T2 are identified without mutual interference, with largely preserved electromagnetic responses to T2. The results suggest parallel brain responses to target events in different sensory modalities. PMID:26084914

  8. Defining Features of Steady-State Timbres

    NASA Astrophysics Data System (ADS)

    Hall, Michael D.

    1995-01-01

    Three experiments were conducted to define steady -state features of timbre for a group of well-trained musicians. Experiment 1 evaluated whether or not pairs of three critical dimensions of timbre--spectral slope (6 or 12 dB/octave), formant structure (/a/ or /i/ vowel), and inharmonicity of partials (harmonic or inharmonic)--were processed in a separable or integral fashion. Accuracy and speed for classification of values along one dimension were examined under different conditions of variability along a second dimension (fixed, correlated, or orthogonal). Spectral slope and formant structure were integral, with classification speed for the target dimension depending upon variability along the orthogonal dimension. In contrast, evidence of asymmetric separability was obtained for inharmonicity. Classification speed for slope and formant structure did not depend on inharmonicity, whereas RT for the target dimension of inharmonicity was strongly influenced by variability along either slope or formant structure. Since the results of Experiment 1 provided a basis for manipulating spectral slope and formant structure as a single feature, these dimensions were correlated in Experiment 2. Subjects searched for targets containing potential features of timbre within arrays of 1-4 inharmonic distractor pitches. Distractors were homogeneous with respect to the dimensions of timbre. When targets had /a/ formants with shallow spectral slopes, search time increased nonlinearly with array size in a manner consistent with the parallel processing of items, and thus feature search. Feature search was not obtained for targets with /i/ formants and steep slopes. Thus, the feature was coded as the presence or absence of /a/ formants with shallow spectral slopes. A search task using heterogeneous distractor values along slope/formant structure was used in Experiment 3 to evaluate whether or not the feature of timbre and pitch were automatically conjoined (integral). Search times for

  9. Entropy Production and Non-Equilibrium Steady States

    NASA Astrophysics Data System (ADS)

    Suzuki, Masuo

    2013-01-01

    The long-term issue of entropy production in transport phenomena is solved by separating the symmetry of the non-equilibrium density matrix ρ(t) in the von Neumann equation, as ρ(t) = ρs(t) + ρa(t) with the symmetric part ρs(t) and antisymmetric part ρa(t). The irreversible entropy production (dS/dt)irr is given in M. Suzuki, Physica A 390(2011)1904 by (dS/dt)irr = Tr( {H}(dρ s{(t)/dt))}/T for the Hamiltonian {H} of the relevant system. The general formulation of the extended von Neumann equation with energy supply and heat extraction is reviewed from the author's paper (M. S.,Physica A391(2012)1074). irreversibility; entropy production; transport phenomena; electric conduction; thermal conduction; linear response; Kubo formula; steady state; non-equilibrium density matrix; energy supply; symmetry-separated von Neumann equation; unboundedness.

  10. The steady-state assumption in oscillating and growing systems.

    PubMed

    Reimers, Alexandra-M; Reimers, Arne C

    2016-10-01

    The steady-state assumption, which states that the production and consumption of metabolites inside the cell are balanced, is one of the key aspects that makes an efficient analysis of genome-scale metabolic networks possible. It can be motivated from two different perspectives. In the time-scales perspective, we use the fact that metabolism is much faster than other cellular processes such as gene expression. Hence, the steady-state assumption is derived as a quasi-steady-state approximation of the metabolism that adapts to the changing cellular conditions. In this article we focus on the second perspective, stating that on the long run no metabolite can accumulate or deplete. In contrast to the first perspective it is not immediately clear how this perspective can be captured mathematically and what assumptions are required to obtain the steady-state condition. By presenting a mathematical framework based on the second perspective we demonstrate that the assumption of steady-state also applies to oscillating and growing systems without requiring quasi-steady-state at any time point. However, we also show that the average concentrations may not be compatible with the average fluxes. In summary, we establish a mathematical foundation for the steady-state assumption for long time periods that justifies its successful use in many applications. Furthermore, this mathematical foundation also pinpoints unintuitive effects in the integration of metabolite concentrations using nonlinear constraints into steady-state models for long time periods. PMID:27363728

  11. Steady-state creep of metal-ceramic multilayered materials

    SciTech Connect

    Shen, Y.L.; Suresh, S.

    1996-04-01

    A general approach is presented for analyzing the steady-state creep response and its underlying mechanisms in metal-ceramic multilayers subjected to monotonic or cyclic variations in temperature. This approach combines the plate or beam theories of continuum mechanics with the mechanism-based classical constitutive equations for steady-state creep. The method is capable of predicting the evolution of overall curvature in the layered solid, the generation of thermal stresses within each layer, and the dominant deformation mechanisms at any through-thickness location of each layer at any instant of time or temperature for prescribed layer geometries, thermo-mechanical properties of the constituent layers, and the applied thermal history. Simulations are presented for Al-Al{sub 2}O{sub 3} bilayer and Al{sub 2}O{sub 3}-Al-Al{sub 2}O{sub 3} trilayer model systems. The predicted results are compared with appropriate experimental measurements for the bilayers subjected to thermal cycling up to 450 C. It is found that the multilayer creep calculations capture the essential features of cyclic thermal response; the extent of stress relaxation in the Al layer, however, is somewhat overestimated, especially at higher temperatures. Possible reasons for such discrepancy are discussed, and the significance and limitations of the overall approach are highlighted. The effects of the rate of heating or cooling on deformation, and the correlations between the present creep analyses and rate-independent elastoplastic formulations for multilayers are also considered. The influence of layer thickness on the evolution of creep mechanisms is also examined from thick multilayers to the limiting case of a thin metallic film on a brittle substrate.

  12. Adaptation of the Steady-state PERG in Early Glaucoma

    PubMed Central

    Porciatti, Vittorio; Bosse, Brandon; Parekh, Prashant K.; Shif, Olga A.; Feuer, William J.; Ventura, Lori M.

    2013-01-01

    Purpose Previous studies have shown that the onset of high-contrast, fast reversing patterned stimuli induces rapid blood flow increase in retinal vessels in association with slow changes of the steady-state PERG signal. We tested the hypothesis that adaptive PERG changes of normal controls (NC) differed from those of glaucoma suspects (GS) and patients with early manifest glaucoma (EMG). Methods Subjects were 42 GS (SAP MD −0.89 ±1.8 dB), 22 EMG (MD −2.12 ±2.4 dB) with visual acuity of ≥20/20 and 16 age-matched NC from a previous study. The PERG signal was sampled every ~15 s over 4 minutes in response to gratings (1.6 cyc/deg, 100% contrast) reversing 16.28 times/s. Amplitude/phase values of successive PERG samples were fitted with a non-parametric LOWESS smoothing function to retrieve the initial and final values and calculate their difference (delta) and the residual standard deviation around the fitted function (SDr). The magnitude of PERG adaptive change compared to random variability was calculated as log10 of percentage coefficient of variation CoV=100*SDr ÷ |delta|. Grand-average PERGs were also obtained by averaging all samples of the same series. Results The grand-average PERG amplitude (ANOVA, p=0.02), but not phase (ANOVA, p=0.63), decreased with increasing severity of disease. Adaptive changes (log10 (CoV) of PERG amplitude were not significantly associated with disease severity (ANOVA, p=0.27), but adaptive changes (log10 (CoV) of PERG phase were (ANOVA, p=0.037; linear trend, p=0.011). Conclusions The steady-state PERG signal displayed slow adaptive changes over time that could be isolated from random variability. PERG adaptive changes differed from those of grand-average PERGs (corresponding the standard steady-state PERG), thus representing a new source of biological information about retinal ganglion cell function that may have potential in the study of glaucoma and optic nerve diseases. PMID:23429613

  13. Automatic hearing loss detection system based on auditory brainstem response

    NASA Astrophysics Data System (ADS)

    Aldonate, J.; Mercuri, C.; Reta, J.; Biurrun, J.; Bonell, C.; Gentiletti, G.; Escobar, S.; Acevedo, R.

    2007-11-01

    Hearing loss is one of the pathologies with the highest prevalence in newborns. If it is not detected in time, it can affect the nervous system and cause problems in speech, language and cognitive development. The recommended methods for early detection are based on otoacoustic emissions (OAE) and/or auditory brainstem response (ABR). In this work, the design and implementation of an automated system based on ABR to detect hearing loss in newborns is presented. Preliminary evaluation in adults was satisfactory.

  14. Auditory brainstem responses in patients under treatment of hemodialysis.

    PubMed

    Aspris, Andreas K; Thodi, Chryssoula D; Balatsouras, Dimitrios G; Thodis, Elias D; Vargemezis, Vassilis; Danielides, Vassilis

    2008-01-01

    This study evaluated the effects of end stage chronic renal failure (CRF) on auditory function and changes in auditory function following a single session of hemodialysis. The experimental group included 31 patients with end-stage renal failure on chronic hemodialysis. The control group consisted of 31 healthy volunteers. The patients were examined prior to and following a session of hemodialysis. Measurements included pure tone audiometry, tympanometry and acoustic reflex measurements, auditory brainstem responses (ABR), and blood now chemistry parameters. Controls underwent the same test battery, with the exception of biochemical and hematological assessment. Prior to hemodialysis sessions, all ABR latencies except interpeak latency I-III were significantly prolonged in the experimental group. A comparison between controls and the experimental group following hemodialysis indicated that wave V absolute latency and interpeak latencies III-V and I-V were significantly prolonged in the slow repetition rate paradigm. In the fast repetition rate, absolute latencies of waves I and V and III-V interpeak latencies were prolonged in the experimental group. Comparison of ABR recordings prior to and following hemodialysis showed overall significant difference between the measures. Post hoc analysis showed a significant improvement in wave I and V latencies in the slow repetition rate and wave V latency in the fast repetition rate. This study showed that neural conduction along the auditory pathway is delayed in patients with end stage CRF as compared to healthy subjects. Dialysis sessions improve overall neural auditory function. However, patients with end stage CRF show delayed conduction even after a session of hemodialysis. PMID:18569911

  15. GABAergic inhibition shapes SAM responses in rat auditory thalamus.

    PubMed

    Cai, R; Caspary, D M

    2015-07-23

    Auditory thalamus (medial geniculate body [MGB]) receives ascending inhibitory GABAergic inputs from inferior colliculus (IC) and descending GABAergic projections from the thalamic reticular nucleus (TRN) with both inputs postulated to play a role in shaping temporal responses. Previous studies suggested that enhanced processing of temporally rich stimuli occurs at the level of MGB, with our recent study demonstrating enhanced GABA sensitivity in MGB compared to IC. The present study used sinusoidal amplitude-modulated (SAM) stimuli to generate modulation transfer functions (MTFs), to examine the role of GABAergic inhibition in shaping the response properties of MGB single units in anesthetized rats. Rate MTFs (rMTFs) were parsed into "bandpass (BP)", "mixed (Mixed)", "highpass (HP)" or "atypical" response types, with most units showing the Mixed response type. GABAA receptor blockade with iontophoretic application of the GABAA receptor (GABAAR) antagonist gabazine (GBZ) selectively altered the response properties of most MGB neurons examined. Mixed and HP units showed significant GABAAR-mediated SAM-evoked rate response changes at higher modulation frequencies (fms), which were also altered by N-methyl-d-aspartic acid (NMDA) receptor blockade (2R)-amino-5-phosphonopentanoate (AP5). BP units, and the lower arm of Mixed units responded to GABAAR blockade with increased responses to SAM stimuli at or near the rate best modulation frequency (rBMF). The ability of GABA circuits to shape responses at higher modulation frequencies is an emergent property of MGB units, not observed at lower levels of the auditory pathway and may reflect activation of MGB NMDA receptors (Rabang and Bartlett, 2011; Rabang et al., 2012). Together, GABAARs exert selective rate control over selected fms, generally without changing the units' response type. These results showed that coding of modulated stimuli at the level of auditory thalamus is at least, in part, strongly controlled by GABA

  16. Steady states and stability in metabolic networks without regulation.

    PubMed

    Ivanov, Oleksandr; van der Schaft, Arjan; Weissing, Franz J

    2016-07-21

    Metabolic networks are often extremely complex. Despite intensive efforts many details of these networks, e.g., exact kinetic rates and parameters of metabolic reactions, are not known, making it difficult to derive their properties. Considerable effort has been made to develop theory about properties of steady states in metabolic networks that are valid for any values of parameters. General results on uniqueness of steady states and their stability have been derived with specific assumptions on reaction kinetics, stoichiometry and network topology. For example, deep results have been obtained under the assumptions of mass-action reaction kinetics, continuous flow stirred tank reactors (CFSTR), concordant reaction networks and others. Nevertheless, a general theory about properties of steady states in metabolic networks is still missing. Here we make a step further in the quest for such a theory. Specifically, we study properties of steady states in metabolic networks with monotonic kinetics in relation to their stoichiometry (simple and general) and the number of metabolites participating in every reaction (single or many). Our approach is based on the investigation of properties of the Jacobian matrix. We show that stoichiometry, network topology, and the number of metabolites that participate in every reaction have a large influence on the number of steady states and their stability in metabolic networks. Specifically, metabolic networks with single-substrate-single-product reactions have disconnected steady states, whereas in metabolic networks with multiple-substrates-multiple-product reactions manifolds of steady states arise. Metabolic networks with simple stoichiometry have either a unique globally asymptotically stable steady state or asymptotically stable manifolds of steady states. In metabolic networks with general stoichiometry the steady states are not always stable and we provide conditions for their stability. In order to demonstrate the biological

  17. Laryngeal electromyographic responses to perturbations in voice pitch auditory feedback

    PubMed Central

    Liu, Hanjun; Behroozmand, Roozbeh; Bove, Michel; Larson, Charles R

    2011-01-01

    The present study was conducted to test the hypothesis that intrinsic laryngeal muscles are involved in producing voice fundamental frequency (F0) responses to perturbations in voice pitch auditory feedback. Electromyography (EMG) recordings of the cricothyroid and thyroarytenoid muscles were made with hooked-wire electrodes, while subjects sustained vowel phonations at three different voice F0 levels (conversational, high pitch in head register, and falsetto register) and received randomized pitch shifts (±100 or ±300 cents) in their voice auditory feedback. The median latencies from stimulus onset to the peak in the EMG and voice F0 responses were 167 and 224 ms, respectively. Among the three different F0 levels, the falsetto register produced compensatory EMG responses that occurred prior to vocal responses and increased along with rising voice F0 responses and decreased for falling F0 responses. For the conversational and high voice levels, the EMG response timing was more variable than in the falsetto voice, and changes in EMG activity with relevance to the vocal responses did not follow the consistent trend observed in the falsetto condition. The data from the falsetto condition suggest that both the cricothyroid and thyroarytenoid muscles are involved in generating the compensatory vocal responses to pitch-shifted voice feedback. PMID:21682416

  18. Auditory evoked off-response: its source distribution is different from that of on-response.

    PubMed

    Noda, K; Tonoike, M; Doi, K; Koizuka, I; Yamaguchi, M; Seo, R; Matsumoto, N; Noiri, T; Takeda, N; Kubo, T

    1998-08-01

    Offset auditory responses were investigated by electroencephalography mainly in the 1970s, but since then no particular attention has been paid to them. Among the studies using magnetoencephalography (MEG) devices there are, to our knowledge, only three studies of the auditory off-response, and no significant variance has ever been observed between the source locations of on- and off-responses elicited from pure tones. We measured auditory evoked magnetic fields (AEFs) to various frequency pure tone stimulation in 5 healthy subjects with a 122-channel helmet-shaped magnetometer, and compared the distributions of the source locations of auditory N100m-Off (magnetic off-response around 100 ms) with those of N100m-On. Their spatial distributions were quite close to each other, and yet they were significantly different. PMID:9721944

  19. Steady-state decoupling and design of linear multivariable systems

    NASA Technical Reports Server (NTRS)

    Thaler, G. J.

    1974-01-01

    A constructive criterion for decoupling the steady states of a linear time-invariant multivariable system is presented. This criterion consists of a set of inequalities which, when satisfied, will cause the steady states of a system to be decoupled. Stability analysis and a new design technique for such systems are given. A new and simple connection between single-loop and multivariable cases is found. These results are then applied to the compensation design for NASA STOL C-8A aircraft. Both steady-state decoupling and stability are justified through computer simulations.

  20. A Note on Equations for Steady-State Optimal Landscapes

    SciTech Connect

    Liu, H.H.

    2010-06-15

    Based on the optimality principle (that the global energy expenditure rate is at its minimum for a given landscape under steady state conditions) and calculus of variations, we have derived a group of partial differential equations for describing steady-state optimal landscapes without explicitly distinguishing between hillslopes and channel networks. Other than building on the well-established Mining's equation, this work does not rely on any empirical relationships (such as those relating hydraulic parameters to local slopes). Using additional constraints, we also theoretically demonstrate that steady-state water depth is a power function of local slope, which is consistent with field data.

  1. Autonomous quantum thermal machine for generating steady-state entanglement

    NASA Astrophysics Data System (ADS)

    Bohr Brask, Jonatan; Haack, Géraldine; Brunner, Nicolas; Huber, Marcus

    2015-11-01

    We discuss a simple quantum thermal machine for the generation of steady-state entanglement between two interacting qubits. The machine is autonomous in the sense that it uses only incoherent interactions with thermal baths, but no source of coherence or external control. By weakly coupling the qubits to thermal baths at different temperatures, inducing a heat current through the system, steady-state entanglement is generated far from thermal equilibrium. Finally, we discuss two possible implementations, using superconducting flux qubits or a semiconductor double quantum dot. Experimental prospects for steady-state entanglement are promising in both systems.

  2. Auditory ERP response to successive stimuli in infancy

    PubMed Central

    Peter, Varghese; Burnham, Denis

    2016-01-01

    Background. Auditory Event-Related Potentials (ERPs) are useful for understanding early auditory development among infants, as it allows the collection of a relatively large amount of data in a short time. So far, studies that have investigated development in auditory ERPs in infancy have mainly used single sounds as stimuli. Yet in real life, infants must decode successive rather than single acoustic events. In the present study, we tested 4-, 8-, and 12-month-old infants’ auditory ERPs to musical melodies comprising three piano notes, and examined ERPs to each individual note in the melody. Methods. Infants were presented with 360 repetitions of a three-note melody while EEG was recorded from 128 channels on the scalp through a Geodesic Sensor Net. For each infant, both latency and amplitude of auditory components P1 and N2 were measured from averaged ERPs for each individual note. Results. Analysis was restricted to response collected at frontal central site. For all three notes, there was an overall reduction in latency for both P1 and N2 over age. For P1, latency reduction was significant from 4 to 8 months, but not from 8 to 12 months. N2 latency, on the other hand, decreased significantly from 4 to 8 to 12 months. With regard to amplitude, no significant change was found for either P1 or N2. Nevertheless, the waveforms of the three age groups were qualitatively different: for the 4-month-olds, the P1–N2 deflection was attenuated for the second and the third notes; for the 8-month-olds, such attenuation was observed only for the middle note; for the 12-month-olds, the P1 and N2 peaks show relatively equivalent amplitude and peak width across all three notes. Conclusion. Our findings indicate that the infant brain is able to register successive acoustic events in a stream, and ERPs become better time-locked to each composite event over age. Younger infants may have difficulties in responding to late occurring events in a stream, and the onset response to

  3. Auditory ERP response to successive stimuli in infancy.

    PubMed

    Chen, Ao; Peter, Varghese; Burnham, Denis

    2016-01-01

    Background. Auditory Event-Related Potentials (ERPs) are useful for understanding early auditory development among infants, as it allows the collection of a relatively large amount of data in a short time. So far, studies that have investigated development in auditory ERPs in infancy have mainly used single sounds as stimuli. Yet in real life, infants must decode successive rather than single acoustic events. In the present study, we tested 4-, 8-, and 12-month-old infants' auditory ERPs to musical melodies comprising three piano notes, and examined ERPs to each individual note in the melody. Methods. Infants were presented with 360 repetitions of a three-note melody while EEG was recorded from 128 channels on the scalp through a Geodesic Sensor Net. For each infant, both latency and amplitude of auditory components P1 and N2 were measured from averaged ERPs for each individual note. Results. Analysis was restricted to response collected at frontal central site. For all three notes, there was an overall reduction in latency for both P1 and N2 over age. For P1, latency reduction was significant from 4 to 8 months, but not from 8 to 12 months. N2 latency, on the other hand, decreased significantly from 4 to 8 to 12 months. With regard to amplitude, no significant change was found for either P1 or N2. Nevertheless, the waveforms of the three age groups were qualitatively different: for the 4-month-olds, the P1-N2 deflection was attenuated for the second and the third notes; for the 8-month-olds, such attenuation was observed only for the middle note; for the 12-month-olds, the P1 and N2 peaks show relatively equivalent amplitude and peak width across all three notes. Conclusion. Our findings indicate that the infant brain is able to register successive acoustic events in a stream, and ERPs become better time-locked to each composite event over age. Younger infants may have difficulties in responding to late occurring events in a stream, and the onset response to the

  4. A comparison of auditory brainstem responses across diving bird species

    USGS Publications Warehouse

    Crowell, Sara E.; Berlin, Alicia; Carr, Catherine E; Olsen, Glenn H.; Therrien, Ronald E; Yannuzzi, Sally E; Ketten, Darlene R

    2015-01-01

    There is little biological data available for diving birds because many live in hard-to-study, remote habitats. Only one species of diving bird, the black-footed penguin (Spheniscus demersus), has been studied in respect to auditory capabilities (Wever et al., Proc Natl Acad Sci USA 63:676–680, 1969). We, therefore, measured in-air auditory threshold in ten species of diving birds, using the auditory brainstem response (ABR). The average audiogram obtained for each species followed the U-shape typical of birds and many other animals. All species tested shared a common region of the greatest sensitivity, from 1000 to 3000 Hz, although audiograms differed significantly across species. Thresholds of all duck species tested were more similar to each other than to the two non-duck species tested. The red-throated loon (Gavia stellata) and northern gannet (Morus bassanus) exhibited the highest thresholds while the lowest thresholds belonged to the duck species, specifically the lesser scaup (Aythya affinis) and ruddy duck (Oxyura jamaicensis). Vocalization parameters were also measured for each species, and showed that with the exception of the common eider (Somateria mollisima), the peak frequency, i.e., frequency at the greatest intensity, of all species' vocalizations measured here fell between 1000 and 3000 Hz, matching the bandwidth of the most sensitive hearing range.

  5. A comparison of auditory brainstem responses across diving bird species

    PubMed Central

    Crowell, Sara E.; Wells-Berlin, Alicia M.; Carr, Catherine E.; Olsen, Glenn H.; Therrien, Ronald E.; Yannuzzi, Sally E.; Ketten, Darlene R.

    2015-01-01

    There is little biological data available for diving birds because many live in hard-to-study, remote habitats. Only one species of diving bird, the black-footed penguin (Spheniscus demersus), has been studied in respect to auditory capabilities (Wever et al. 1969). We therefore measured in-air auditory threshold in ten species of diving birds, using the auditory brainstem response (ABR). The average audiogram obtained for each species followed the U-shape typical of birds and many other animals. All species tested shared a common region of greatest sensitivity, from 1000 to 3000 Hz, although audiograms differed significantly across species. Thresholds of all duck species tested were more similar to each other than to the two non-duck species tested. The red-throated loon (Gavia stellata) and northern gannet (Morus bassanus) exhibited the highest thresholds while the lowest thresholds belonged to the duck species, specifically the lesser scaup (Aythya affinis) and ruddy duck (Oxyura jamaicensis). Vocalization parameters were also measured for each species, and showed that with the exception of the common eider (Somateria mollisima), the peak frequency, i.e. frequency at the greatest intensity, of all species’ vocalizations measured here fell between 1000 and 3000 Hz, matching the bandwidth of the most sensitive hearing range. PMID:26156644

  6. A comparison of auditory brainstem responses across diving bird species.

    PubMed

    Crowell, Sara E; Wells-Berlin, Alicia M; Carr, Catherine E; Olsen, Glenn H; Therrien, Ronald E; Yannuzzi, Sally E; Ketten, Darlene R

    2015-08-01

    There is little biological data available for diving birds because many live in hard-to-study, remote habitats. Only one species of diving bird, the black-footed penguin (Spheniscus demersus), has been studied in respect to auditory capabilities (Wever et al., Proc Natl Acad Sci USA 63:676-680, 1969). We, therefore, measured in-air auditory threshold in ten species of diving birds, using the auditory brainstem response (ABR). The average audiogram obtained for each species followed the U-shape typical of birds and many other animals. All species tested shared a common region of the greatest sensitivity, from 1000 to 3000 Hz, although audiograms differed significantly across species. Thresholds of all duck species tested were more similar to each other than to the two non-duck species tested. The red-throated loon (Gavia stellata) and northern gannet (Morus bassanus) exhibited the highest thresholds while the lowest thresholds belonged to the duck species, specifically the lesser scaup (Aythya affinis) and ruddy duck (Oxyura jamaicensis). Vocalization parameters were also measured for each species, and showed that with the exception of the common eider (Somateria mollisima), the peak frequency, i.e., frequency at the greatest intensity, of all species' vocalizations measured here fell between 1000 and 3000 Hz, matching the bandwidth of the most sensitive hearing range. PMID:26156644

  7. Amelioration of Auditory Response by DA9801 in Diabetic Mouse

    PubMed Central

    Hong, Bin Na; Her, You Ri; Castañeda, Rodrigo; Moon, Hyo Won

    2015-01-01

    Diabetes mellitus (DM) is a metabolic disease that involves disorders such as diabetic retinopathy, diabetic neuropathy, and diabetic hearing loss. Recently, neurotrophin has become a treatment target that has shown to be an attractive alternative in recovering auditory function altered by DM. The aim of this study was to evaluate the effect of DA9801, a mixture of Dioscorea nipponica and Dioscorea japonica extracts, in the auditory function damage produced in a STZ-induced diabetic model and to provide evidence of the mechanisms involved in enhancing these protective effects. We found a potential application of DA9801 on hearing impairment in the STZ-induced diabetic model, demonstrated by reducing the deterioration produced by DM in ABR threshold in response to clicks and normalizing wave I–IV latencies and Pa latencies in AMLR. We also show evidence that these effects might be elicited by inducing NGF related through Nr3c1 and Akt. Therefore, this result suggests that the neuroprotective effects of DA9801 on the auditory damage produced by DM may be affected by NGF increase resulting from Nr3c1 via Akt transformation. PMID:25878713

  8. Amelioration of Auditory Response by DA9801 in Diabetic Mouse.

    PubMed

    Lee, Yeong Ro; Hong, Bin Na; Her, You Ri; Castañeda, Rodrigo; Moon, Hyo Won; Kang, Tong Ho

    2015-01-01

    Diabetes mellitus (DM) is a metabolic disease that involves disorders such as diabetic retinopathy, diabetic neuropathy, and diabetic hearing loss. Recently, neurotrophin has become a treatment target that has shown to be an attractive alternative in recovering auditory function altered by DM. The aim of this study was to evaluate the effect of DA9801, a mixture of Dioscorea nipponica and Dioscorea japonica extracts, in the auditory function damage produced in a STZ-induced diabetic model and to provide evidence of the mechanisms involved in enhancing these protective effects. We found a potential application of DA9801 on hearing impairment in the STZ-induced diabetic model, demonstrated by reducing the deterioration produced by DM in ABR threshold in response to clicks and normalizing wave I-IV latencies and Pa latencies in AMLR. We also show evidence that these effects might be elicited by inducing NGF related through Nr3c1 and Akt. Therefore, this result suggests that the neuroprotective effects of DA9801 on the auditory damage produced by DM may be affected by NGF increase resulting from Nr3c1 via Akt transformation. PMID:25878713

  9. Neural Responses to Complex Auditory Rhythms: The Role of Attending

    PubMed Central

    Chapin, Heather L.; Zanto, Theodore; Jantzen, Kelly J.; Kelso, Scott J. A.; Steinberg, Fred; Large, Edward W.

    2010-01-01

    The aim of this study was to explore the role of attention in pulse and meter perception using complex rhythms. We used a selective attention paradigm in which participants attended to either a complex auditory rhythm or a visually presented word list. Performance on a reproduction task was used to gauge whether participants were attending to the appropriate stimulus. We hypothesized that attention to complex rhythms – which contain no energy at the pulse frequency – would lead to activations in motor areas involved in pulse perception. Moreover, because multiple repetitions of a complex rhythm are needed to perceive a pulse, activations in pulse-related areas would be seen only after sufficient time had elapsed for pulse perception to develop. Selective attention was also expected to modulate activity in sensory areas specific to the modality. We found that selective attention to rhythms led to increased BOLD responses in basal ganglia, and basal ganglia activity was observed only after the rhythms had cycled enough times for a stable pulse percept to develop. These observations suggest that attention is needed to recruit motor activations associated with the perception of pulse in complex rhythms. Moreover, attention to the auditory stimulus enhanced activity in an attentional sensory network including primary auditory cortex, insula, anterior cingulate, and prefrontal cortex, and suppressed activity in sensory areas associated with attending to the visual stimulus. PMID:21833279

  10. Evidence for the possible involvement of calmodulin in regulation of steady state levels of Hsp90 family members (Hsp87 and Hsp85) in response to heat shock in sorghum

    PubMed Central

    Virdi, Amardeep Singh; Pareek, Ashwani

    2011-01-01

    Pharmacological studies, using Ca2+ channel blockers (LaCl3 and verapamil) and calmodulin (CaM) antagonists (CPZ and W7), were carried out to understand the role of Ca2+/CaM in the regulation of heat shock-induced expression of Hsp90 (Hsp87 and Hsp85) and Hsp70 (Hsp75 and Hsp73) members in sorghum. It was observed that the expression of both Hsp87 and Hsp85 proteins was decreased in presence of Ca2+ channel blockers and CaM antagonists, under both control and heat stress conditions, as contrary to the steady state levels of Hsp75 and Hsp73, which were not affected significantly under similar conditions. Further, the exposure of sorghum seedlings to geldanamycin, a specific inhibitor of Hsp90, resulted in induction of Hsp87 and Hsp85 in the absence of heat shock also. This study provides the first evidence suggesting that in plants, the in vivo expression of Hsp90 (Hsp87 and Hsp85) is likely to be modulated by Ca2+/CaM under normal and thermal stress conditions. The likely implications of these findings are discussed. PMID:21336025

  11. The steady-state visual evoked potential in vision research: A review

    PubMed Central

    Norcia, Anthony M.; Appelbaum, L. Gregory; Ales, Justin M.; Cottereau, Benoit R.; Rossion, Bruno

    2015-01-01

    Periodic visual stimulation and analysis of the resulting steady-state visual evoked potentials were first introduced over 80 years ago as a means to study visual sensation and perception. From the first single-channel recording of responses to modulated light to the present use of sophisticated digital displays composed of complex visual stimuli and high-density recording arrays, steady-state methods have been applied in a broad range of scientific and applied settings.The purpose of this article is to describe the fundamental stimulation paradigms for steady-state visual evoked potentials and to illustrate these principles through research findings across a range of applications in vision science. PMID:26024451

  12. An Operational Definition of the Steady State in Enzyme Kinetics.

    ERIC Educational Resources Information Center

    Barnsley, E. A.

    1990-01-01

    The Briggs-Haldane assumption is used as the basis for the development of a kinetic model for enzyme catalysis. An alternative definition of the steady state and examples of realistic mechanisms are provided. (KR)

  13. Steady state model of electrochemical gas sensors with multiple reactions

    SciTech Connect

    Brailsford, A.D.; Yussouff, M.; Logothetis, E.M.

    1996-12-31

    A general first-principles model of the steady state response of metal oxide gas sensors was developed by the authors and applied to the case of both electrochemical and resistive type oxygen sensors. It can describe many features of the experimentally observed response of commercial electrochemical zirconia sensors exposed to non-equilibrium gas mixtures consisting of O{sub 2} and one or more reducing species (CO, H{sub 2} , etc). However, the calculated sensor emf as a function of R`= 2p{sub O2}/P{sub CO} (or 2p{sub O2}/P{sub H2}) always showed a sharp transition from high to low values at some R` value and had a small value for R` >> 1. These results do not agree with the broad transitions and relatively high emf values for large R`, as observed experimentally at low temperatures. This paper discusses an extension of the model which is able to describe all aspects of the observed response.

  14. Non-constant positive steady-states of a diffusive predator-prey system in homogeneous environment

    NASA Astrophysics Data System (ADS)

    Ko, Wonlyul; Ryu, Kimun

    2007-03-01

    In this paper, we investigate the existence and non-existence of non-constant positive steady-states of a diffusive predator-prey interaction system under homogeneous Neumann boundary condition. In homogeneous environment, we show that the predator-prey model with Leslie-Gower functional response has no non-constant positive solution, but the system with a general functional response may have at least one non-constant positive steady-state under some conditions.

  15. Abnormal Attention in Autism Shown by Steady-State Visual Evoked Potentials.

    ERIC Educational Resources Information Center

    Belmonte, Matthew

    2000-01-01

    Eight males with autism were required to shift attention between rapidly flashed targets alternating between left and right visual hemifields. When targets were separated by less than 700 ms, steady-state brain electrical response in both hemispheres was augmented and background EEG decreased for rightward shifts as compared with leftward shifts.…

  16. ROLE OF NMDA, NICOTINIC, AND GABA RECEPTORS IN THE STEADY STATE VISUAL EVOKED POTENTIAL IN RATS.

    EPA Science Inventory

    This manuscript characterizes the receptor pathways involved in pattern-evoked potential generation in rats

    " NMDA and nicotinic acetylcholine receptors appear to be involved in the generation of the steady-state pattern evoked response in vivo.

    " The pattern evok...

  17. Decoding stimulus duration from neural responses in the auditory midbrain

    PubMed Central

    Aubie, Brandon; Sayegh, Riziq; Fremouw, Thane; Covey, Ellen

    2014-01-01

    Neurons with responses selective for the duration of an auditory stimulus are called duration-tuned neurons (DTNs). Temporal specificity in their spiking suggests that one function of DTNs is to encode stimulus duration; however, the efficacy of duration encoding by DTNs has yet to be investigated. Herein, we characterize the information content of individual cells and a population of DTNs from the mammalian inferior colliculus (IC) by measuring the stimulus-specific information (SSI) and estimated Fisher information (FI) of spike count responses. We found that SSI was typically greatest for those stimulus durations that evoked maximum spike counts, defined as best duration (BD) stimuli, and that FI was maximal for stimulus durations off BD where sensitivity to a change in duration was greatest. Using population data, we demonstrate that a maximum likelihood estimator (MLE) can accurately decode stimulus duration from evoked spike counts. We also simulated a two-alternative forced choice task by having MLE models decide whether two durations were the same or different. With this task we measured the just-noticeable difference threshold for stimulus duration and calculated the corresponding Weber fractions across the stimulus domain. Altogether, these results demonstrate that the spiking responses of DTNs from the mammalian IC contain sufficient information for the CNS to encode, decode, and discriminate behaviorally relevant auditory signal durations. PMID:25122706

  18. Auditory middle latency response in children with learning difficulties

    PubMed Central

    Frizzo, Ana Claudia Figueiredo; Issac, Myriam Lima; Pontes-Fernandes, Angela Cristina; Menezes, Pedro de Lemos; Funayama, Carolina Araújo Rodrigues

    2012-01-01

    Summary Introduction: This is an objective laboratory assessment of the central auditory systems of children with learning disabilities. Aim: To examine and determine the properties of the components of the Auditory Middle Latency Response in a sample of children with learning disabilities. Methods: This was a prospective, cross-sectional cohort study with quantitative, descriptive, and exploratory outcomes. We included 50 children aged 8–13 years of both genders with and without learning disorders. Those with disorders of known organic, environmental, or genetic causes were excluded. Results and Conclusions: The Na, Pa, and Nb waves were identified in all subjects. The ranges of the latency component values were as follows: Na = 9.8–32.3 ms, Pa = 19.0–51.4 ms, Nb = 30.0–64.3 ms (learning disorders group) and Na = 13.2–29.6 ms, Pa = 21.8–42.8 ms, Nb = 28.4–65.8 ms (healthy group). The values of the Na-Pa amplitude ranged from 0.3 to 6.8 ìV (learning disorders group) or 0.2–3.6 ìV (learning disorders group). Upon analysis, the functional characteristics of the groups were distinct: the left hemisphere Nb latency was longer in the study group than in the control group. Peculiarities of the electrophysiological measures were observed in the children with learning disorders. This study has provided information on the Auditory Middle Latency Response and can serve as a reference for other clinical and experimental studies in children with these disorders. PMID:25991954

  19. Multiple steady states in coupled flow tank reactors

    NASA Astrophysics Data System (ADS)

    Hunt, Katharine L. C.; Kottalam, J.; Hatlee, Michael D.; Ross, John

    1992-05-01

    Coupling between continuous-flow, stirred tank reactors (CSTR's), each having multiple steady states, can produce new steady states with different concentrations of the chemical species in each of the coupled tanks. In this work, we identify a kinetic potential ψ that governs the deterministic time evolution of coupled tank reactors, when the reaction mechanism permits a single-variable description of the states of the individual tanks; examples include the iodate-arsenous acid reaction, a cubic model suggested by Noyes, and two quintic models. Stable steady states correspond to minima of ψ, and unstable steady states to maxima or saddle points; marginally stable states typically correspond to saddle-node points. We illustrate the variation in ψ due to changes in the rate constant for external material intake (k0) and for exchange between tanks (kx). For fixed k0 values, we analyze the changes in numbers and types of steady states as kx increases from zero. We show that steady states disappear by pairwise coalescence; we also show that new steady states may appear with increasing kx, when the reaction mechanism is sufficiently complex. For fixed initial conditions, the steady state ultimately reached in a mixing experiment may depend on the exchange rate constant as a function of time, kx(t) : Adiabatic mixing is obtained in the limit of slow changes in kx(t) and instantaneous mixing in the limit as kx(t)→∞ while t remains small. Analyses based on the potential ψ predict the outcome of mixing experiments for arbitrary kx(t). We show by explicit counterexamples that a prior theory developed by Noyes does not correctly predict the instability points or the transitions between steady states of coupled tanks, to be expected in mixing experiments. We further show that the outcome of such experiments is not connected to the relative stability of steady states in individual tank reactors. We find that coupling may effectively stabilize the tanks. We provide

  20. Mechanism of Non-Steady State Dissolution of Goethite in the Presence of Siderophores

    NASA Astrophysics Data System (ADS)

    Reichard, P. U.; Kretzschmar, R.; Kraemer, S. M.

    2003-12-01

    reproducible and the magnitude of dissolved iron corresponds to the reaction time of goethite with oxalate. Analogous non-steady state experiments were conducted, but with two other siderophores or citrate to induce non-steady state conditions: 40 microM of the bacterial siderophore desferrioxamine B (DFO-B), 40 microM of the fungal siderophore Ferrichrome, and 3 mM of citrate. Fast dissolution of iron was observed as a response to non-steady state. We also substituted the non-siderophore ligand oxalate by 500 microM citrate or 750 microM malonate and again observed fast dissolution after the non-steady state siderophore additions. Independent of the type of the ligands, a reproducible fast dissolution of iron followed by steady state dissolution was observed after the addition of the non-steady state ligand concentrations. Thus it can be said that the reproducible fast dissolution of iron under non-steady state conditions represents a general geochemical mechanism and an important process in the context of biological iron acquisition in natural systems. References Marschner, H., Roemheld, V. et al. (1986). "Different Strategies in Higher-Plants in Mobilization and Uptake of Iron". Journal of Plant Nutrition 9(3-7): 695-713. Roemheld, V. and Marschner, H. (1986)." Evidence for a Specific Uptake System for Iron Phytosiderophore in Roots of Grasses". Plant Physiology 80(1): 175-180.

  1. Noise exposure enhances auditory cortex responses related to hyperacusis behavior.

    PubMed

    Sun, Wei; Deng, Anchun; Jayaram, Aditi; Gibson, Brittany

    2012-11-16

    Hyperacusis, a marked intolerance to normal environmental sound, is a common symptom in patients with tinnitus, Williams syndrome, autism, and other neurologic diseases. It has been suggested that an imbalance of excitation and inhibition in the central auditory system (CAS) may play an important role in hyperacusis. Recent studies found that noise exposure, one of the most common causes of hearing loss and tinnitus, can increase the auditory cortex (AC) response, presumably by increasing the gain of the AC. However, it is not clear whether the increased cortical response will affect sound sensitivity and induce hyperacusis. In this experiment, we studied the effects of noise exposure (narrow band noise, 12 kHz, 120 dB SPL, 1 hour) on the physiological response of the inferior colliculus (IC) and the AC, and the behavioral sound reaction in conscious Sprague Dawley rats. Noise exposure induced a decrease of sound evoked potential in the IC. However, significant increases of AC response including sound evoked potentials and the spike firing rates of AC neurons were recorded right after the noise exposure. These results suggest that noise exposure induces hyperexcitability of AC presumably by increasing the post-synaptic response of AC neurons. The behavioral consequence of the noise exposure on sound perception was measured by the amplitude of the acoustic startle response before and after noise exposure in a separate group of rats. Although noise exposure caused a moderate hearing loss, the acoustic startle amplitude at the super-threshold level was significantly increased. These results suggest that noise exposure can cause exaggerated the sound reaction which may be related with the enhanced responsiveness of the AC neurons. This phenomenon may be related with noise induced hyperacusis.This article is part of a Special Issue entitled: Tinnitus Neuroscience. PMID:22402030

  2. Dissociable influences of primary auditory cortex and the posterior auditory field on neuronal responses in the dorsal zone of auditory cortex

    PubMed Central

    Kok, Melanie A.; Stolzberg, Daniel; Brown, Trecia A.

    2014-01-01

    Current models of hierarchical processing in auditory cortex have been based principally on anatomical connectivity while functional interactions between individual regions have remained largely unexplored. Previous cortical deactivation studies in the cat have addressed functional reciprocal connectivity between primary auditory cortex (A1) and other hierarchically lower level fields. The present study sought to assess the functional contribution of inputs along multiple stages of the current hierarchical model to a higher order area, the dorsal zone (DZ) of auditory cortex, in the anaesthetized cat. Cryoloops were placed over A1 and posterior auditory field (PAF). Multiunit neuronal responses to noise burst and tonal stimuli were recorded in DZ during cortical deactivation of each field individually and in concert. Deactivation of A1 suppressed peak neuronal responses in DZ regardless of stimulus and resulted in increased minimum thresholds and reduced absolute bandwidths for tone frequency receptive fields in DZ. PAF deactivation had less robust effects on DZ firing rates and receptive fields compared with A1 deactivation, and combined A1/PAF cooling was largely driven by the effects of A1 deactivation at the population level. These results provide physiological support for the current anatomically based model of both serial and parallel processing schemes in auditory cortical hierarchical organization. PMID:25339709

  3. Dissociable influences of primary auditory cortex and the posterior auditory field on neuronal responses in the dorsal zone of auditory cortex.

    PubMed

    Kok, Melanie A; Stolzberg, Daniel; Brown, Trecia A; Lomber, Stephen G

    2015-01-15

    Current models of hierarchical processing in auditory cortex have been based principally on anatomical connectivity while functional interactions between individual regions have remained largely unexplored. Previous cortical deactivation studies in the cat have addressed functional reciprocal connectivity between primary auditory cortex (A1) and other hierarchically lower level fields. The present study sought to assess the functional contribution of inputs along multiple stages of the current hierarchical model to a higher order area, the dorsal zone (DZ) of auditory cortex, in the anaesthetized cat. Cryoloops were placed over A1 and posterior auditory field (PAF). Multiunit neuronal responses to noise burst and tonal stimuli were recorded in DZ during cortical deactivation of each field individually and in concert. Deactivation of A1 suppressed peak neuronal responses in DZ regardless of stimulus and resulted in increased minimum thresholds and reduced absolute bandwidths for tone frequency receptive fields in DZ. PAF deactivation had less robust effects on DZ firing rates and receptive fields compared with A1 deactivation, and combined A1/PAF cooling was largely driven by the effects of A1 deactivation at the population level. These results provide physiological support for the current anatomically based model of both serial and parallel processing schemes in auditory cortical hierarchical organization. PMID:25339709

  4. [Circadian variation in the latency of auditory brainstem response].

    PubMed

    Murakami, S; Sotsu, M; Nakamura, N

    1992-07-01

    The auditory brainstem response (ABR) has been found to reflect many pathological conditions within the auditory system and brainstem. And now, many neurosurgeons are using it to monitor the integrity of the auditory pathway during neurosurgical procedures. It is said that ABR shows little variation from person to person or laboratory to laboratory, nor is it easily affected by anesthesia, level of consciousness, fluctuation of blood pressure or hypoxemia. On the other hand, previous studies have shown that component waves of the ABR increase in latency and decrease in amplitude with lowered temperature. We reported here that naturally occurring circadian variations in body temperature were correlated with similar changes in the latency of the ABR. Tympanic temperature (Tty), deep forehead temperature (Thd) and ABR were recorded every 3 hours during a 24-hour period for a total of 8 recording sessions from each of 6 healthy persons (2 males and 4 females, mean age 24.3 years). The subjects were free to come and go during the day but slept overnight in the laboratory. All subjects had circadian variations in each temperature on the order of one degree. Thd had a tendency to fluctuate and its range of difference from Tty was -0.5-0.4 degree C. There was a more significant negative correlation between the latency of the ABR and Tty than that of Thd. It has become apparent that ABR latency is affected by small temperature changes such as circadian variation. The rate of a latency change in the ABR was 0.15msec per degree (C).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1329888

  5. Steady state solutions to dynamically loaded periodic structures

    NASA Technical Reports Server (NTRS)

    Kalinowski, A. J.

    1980-01-01

    The general problem of solving for the steady state (time domain) dynamic response (i.e., NASTRAN rigid format-8) of a general elastic periodic structure subject to a phase difference loading of the type encountered in traveling wave propagation problems was studied. Two types of structural configurations were considered; in the first type, the structure has a repeating pattern over a span that is long enough to be considered, for all practical purposes, as infinite; in the second type, the structure has structural rotational symmetry in the circumferential direction. The theory and a corresponding set of DMAP instructions which permits the NASTRAN user to automatically alter the rigid format-8 sequence to solve the intended class of problems are presented. Final results are recovered as with any ordinary rigid format-8 solution, except that the results are only printed for the typical periodic segment of the structure. A simple demonstration problem having a known exact solution is used to illustrate the implementation of the procedure.

  6. Cross-Modal Plasticity in Higher-Order Auditory Cortex of Congenitally Deaf Cats Does Not Limit Auditory Responsiveness to Cochlear Implants

    PubMed Central

    Baumhoff, Peter; Tillein, Jochen; Lomber, Stephen G.; Hubka, Peter; Kral, Andrej

    2016-01-01

    Congenital sensory deprivation can lead to reorganization of the deprived cortical regions by another sensory system. Such cross-modal reorganization may either compete with or complement the “original“ inputs to the deprived area after sensory restoration and can thus be either adverse or beneficial for sensory restoration. In congenital deafness, a previous inactivation study documented that supranormal visual behavior was mediated by higher-order auditory fields in congenitally deaf cats (CDCs). However, both the auditory responsiveness of “deaf” higher-order fields and interactions between the reorganized and the original sensory input remain unknown. Here, we studied a higher-order auditory field responsible for the supranormal visual function in CDCs, the auditory dorsal zone (DZ). Hearing cats and visual cortical areas served as a control. Using mapping with microelectrode arrays, we demonstrate spatially scattered visual (cross-modal) responsiveness in the DZ, but show that this did not interfere substantially with robust auditory responsiveness elicited through cochlear implants. Visually responsive and auditory-responsive neurons in the deaf auditory cortex formed two distinct populations that did not show bimodal interactions. Therefore, cross-modal plasticity in the deaf higher-order auditory cortex had limited effects on auditory inputs. The moderate number of scattered cross-modally responsive neurons could be the consequence of exuberant connections formed during development that were not pruned postnatally in deaf cats. Although juvenile brain circuits are modified extensively by experience, the main driving input to the cross-modally (visually) reorganized higher-order auditory cortex remained auditory in congenital deafness. SIGNIFICANCE STATEMENT In a common view, the “unused” auditory cortex of deaf individuals is reorganized to a compensatory sensory function during development. According to this view, cross-modal plasticity takes

  7. Auditory Brainstem Responses and EMFs Generated by Mobile Phones.

    PubMed

    Khullar, Shilpa; Sood, Archana; Sood, Sanjay

    2013-12-01

    There has been a manifold increase in the number of mobile phone users throughout the world with the current number of users exceeding 2 billion. However this advancement in technology like many others is accompanied by a progressive increase in the frequency and intensity of electromagnetic waves without consideration of the health consequences. The aim of our study was to advance our understanding of the potential adverse effects of GSM mobile phones on auditory brainstem responses (ABRs). 60 subjects were selected for the study and divided into three groups of 20 each based on their usage of mobile phones. Their ABRs were recorded and analysed for latency of waves I-V as well as interpeak latencies I-III, I-V and III-V (in ms). Results revealed no significant difference in the ABR parameters between group A (control group) and group B (subjects using mobile phones for maximum 30 min/day for 5 years). However the latency of waves was significantly prolonged in group C (subjects using mobile phones for 10 years for a maximum of 30 min/day) as compared to the control group. Based on our findings we concluded that long term exposure to mobile phones may affect conduction in the peripheral portion of the auditory pathway. However more research needs to be done to study the long term effects of mobile phones particularly of newer technologies like smart phones and 3G. PMID:24427730

  8. Deviance-Related Responses along the Auditory Hierarchy: Combined FFR, MLR and MMN Evidence

    PubMed Central

    Shiga, Tetsuya; Althen, Heike; Cornella, Miriam; Zarnowiec, Katarzyna; Yabe, Hirooki; Escera, Carles

    2015-01-01

    The mismatch negativity (MMN) provides a correlate of automatic auditory discrimination in human auditory cortex that is elicited in response to violation of any acoustic regularity. Recently, deviance-related responses were found at much earlier cortical processing stages as reflected by the middle latency response (MLR) of the auditory evoked potential, and even at the level of the auditory brainstem as reflected by the frequency following response (FFR). However, no study has reported deviance-related responses in the FFR, MLR and long latency response (LLR) concurrently in a single recording protocol. Amplitude-modulated (AM) sounds were presented to healthy human participants in a frequency oddball paradigm to investigate deviance-related responses along the auditory hierarchy in the ranges of FFR, MLR and LLR. AM frequency deviants modulated the FFR, the Na and Nb components of the MLR, and the LLR eliciting the MMN. These findings demonstrate that it is possible to elicit deviance-related responses at three different levels (FFR, MLR and LLR) in one single recording protocol, highlight the involvement of the whole auditory hierarchy in deviance detection and have implications for cognitive and clinical auditory neuroscience. Moreover, the present protocol provides a new research tool into clinical neuroscience so that the functional integrity of the auditory novelty system can now be tested as a whole in a range of clinical populations where the MMN was previously shown to be defective. PMID:26348628

  9. Experiential Response to Auditory and Visual Hallucination Suggestions in Hypnotic Subjects

    ERIC Educational Resources Information Center

    Spanos, Nicholas P.; And Others

    1976-01-01

    The effects of several attitudinal, cognitive skill, and personality variables in response to auditory and visual hallucination suggestions to hypnotic subjects are assessed. Cooperative attitudes toward hypnosis and involvement in everyday imaginative activities (absorption) correlated with response to auditory and visual hallucination…

  10. Evaluation of a steady state MPD thruster test facility

    SciTech Connect

    Reed, C.B.; Carlson, L.W.; Herman, H.; Doss, E.D.; Kilgore, O.

    1985-01-01

    The successful development of multimegawatt MPD thrusters depends, to a great extent, on testing them under steady state high altitude space conditions. Steady state testing is required to provide thermal characteristics, life cycle, erosion, and other essential data. the major technical obstacle for ground testing of MPD thrusters in a space simulation facility is the inability of state-of-the-art vacuum systems to handle the tremendous pumping speeds required for multimegawatt MPD thrusters. This is true for other types of electric propulsion devices as well. This paper discusses the results of the first phase of an evaluation of steady state MPD thruster test facilities. The first phase addresses the conceptual design of vacuum systems required to support multimegawatt MPD thruster testing. Three advanced pumping system concepts were evaluated and are presented here.

  11. Poissonian steady states: From stationary densities to stationary intensities

    NASA Astrophysics Data System (ADS)

    Eliazar, Iddo

    2012-10-01

    Markov dynamics are the most elemental and omnipresent form of stochastic dynamics in the sciences, with applications ranging from physics to chemistry, from biology to evolution, and from economics to finance. Markov dynamics can be either stationary or nonstationary. Stationary Markov dynamics represent statistical steady states and are quantified by stationary densities. In this paper, we generalize the notion of steady state to the case of general Markov dynamics. Considering an ensemble of independent motions governed by common Markov dynamics, we establish that the entire ensemble attains Poissonian steady states which are quantified by stationary Poissonian intensities and which hold valid also in the case of nonstationary Markov dynamics. The methodology is applied to a host of Markov dynamics, including Brownian motion, birth-death processes, random walks, geometric random walks, renewal processes, growth-collapse dynamics, decay-surge dynamics, Ito diffusions, and Langevin dynamics.

  12. From Steady-State To Cyclic Metal Forming Processes

    NASA Astrophysics Data System (ADS)

    Montmitonnet, Pierre

    2007-05-01

    Continuous processes often exhibit a high proportion of steady state, and have been modeled with steady-state formulations for thirty years, resulting in very CPU-time efficient computations. On the other hand, incremental forming processes generally remain a challenge for FEM software, because of the local nature of deformation compared with the size of the part to be formed, and of the large number of deformation steps needed. Among them however, certain semi-continuous metal forming processes can be characterized as periodic, or cyclic. In this case, an efficient computational strategy can be derived from the ideas behind the steady-state models. This will be illustrated with the example of pilgering, a seamless tube cold rolling process.

  13. Current Pressure Transducer Application of Model-based Prognostics Using Steady State Conditions

    NASA Technical Reports Server (NTRS)

    Teubert, Christopher; Daigle, Matthew J.

    2014-01-01

    Prognostics is the process of predicting a system's future states, health degradation/wear, and remaining useful life (RUL). This information plays an important role in preventing failure, reducing downtime, scheduling maintenance, and improving system utility. Prognostics relies heavily on wear estimation. In some components, the sensors used to estimate wear may not be fast enough to capture brief transient states that are indicative of wear. For this reason it is beneficial to be capable of detecting and estimating the extent of component wear using steady-state measurements. This paper details a method for estimating component wear using steady-state measurements, describes how this is used to predict future states, and presents a case study of a current/pressure (I/P) Transducer. I/P Transducer nominal and off-nominal behaviors are characterized using a physics-based model, and validated against expected and observed component behavior. This model is used to map observed steady-state responses to corresponding fault parameter values in the form of a lookup table. This method was chosen because of its fast, efficient nature, and its ability to be applied to both linear and non-linear systems. Using measurements of the steady state output, and the lookup table, wear is estimated. A regression is used to estimate the wear propagation parameter and characterize the damage progression function, which are used to predict future states and the remaining useful life of the system.

  14. Steady-state CO/sub 2/ laser model

    SciTech Connect

    Scott, M.W.; Myers, G.D.

    1984-09-01

    A steady-state CO/sub 2/ lase model is reported which can be used to predict and evaluate the performance of cw slow-flow and no-flow CO/sub 2/ lasers. Traditional CO/sub 2/ laser models require the solution of several simultaneous differential equations and can be used to model pulsed and fast-flow lasers in addition to cw and slow-flow devices. The model reported here is computationally simpler, requiring only a routine to solve one equation in one unknown, but is only useful for lasers which operate in the steady state.

  15. Non-equilibrium steady state in the hydro regime

    NASA Astrophysics Data System (ADS)

    Pourhasan, Razieh

    2016-02-01

    We study the existence and properties of the non-equilibrium steady state which arises by putting two copies of systems at different temperatures into a thermal contact. We solve the problem for the relativistic systems that are described by the energy-momentum of a perfect hydro with general equation of state (EOS). In particular, we examine several simple examples: a hydro with a linear EOS, a holographic CFT perturbed by a relevant operator and a barotropic fluid, i.e., P=P({E}) . Our studies suggest that the formation of steady state is a universal result of the hydro regime regardless of the kind of fluid.

  16. Steady-state coherent transfer by adiabatic passage.

    PubMed

    Huneke, Jan; Platero, Gloria; Kohler, Sigmund

    2013-01-18

    We propose steady-state electron transport based on coherent transfer by adiabatic passage (CTAP) in a linearly arranged triple quantum dot with leads attached to the outer dots. Its main feature is repeated steering of single electrons from the first dot to the last dot without relevant occupation of the middle dot. The coupling to leads enables a steady-state current, whose shot noise is significantly suppressed provided that the CTAP protocol performs properly. This represents an indication for the direct transfer between spatially separated dots and, thus, may resolve the problem of finding experimental evidence for the nonoccupation of the middle dot. PMID:23373941

  17. Steady-state entanglement activation in optomechanical cavities

    NASA Astrophysics Data System (ADS)

    Farace, Alessandro; Ciccarello, Francesco; Fazio, Rosario; Giovannetti, Vittorio

    2014-02-01

    Quantum discord, and related indicators, are raising a relentless interest as a novel paradigm of nonclassical correlations beyond entanglement. Here, we discover a discord-activated mechanism yielding steady-state entanglement production in a realistic continuous-variable setup. This comprises two coupled optomechanical cavities, where the optical modes (OMs) communicate through a fiber. We first use a simplified model to highlight the creation of steady-state discord between the OMs. We show next that such discord improves the level of stationary optomechanical entanglement attainable in the system, making it more robust against temperature and thermal noise.

  18. Speech training alters consonant and vowel responses in multiple auditory cortex fields

    PubMed Central

    Engineer, Crystal T.; Rahebi, Kimiya C.; Buell, Elizabeth P.; Fink, Melyssa K.; Kilgard, Michael P.

    2015-01-01

    Speech sounds evoke unique neural activity patterns in primary auditory cortex (A1). Extensive speech sound discrimination training alters A1 responses. While the neighboring auditory cortical fields each contain information about speech sound identity, each field processes speech sounds differently. We hypothesized that while all fields would exhibit training-induced plasticity following speech training, there would be unique differences in how each field changes. In this study, rats were trained to discriminate speech sounds by consonant or vowel in quiet and in varying levels of background speech-shaped noise. Local field potential and multiunit responses were recorded from four auditory cortex fields in rats that had received 10 weeks of speech discrimination training. Our results reveal that training alters speech evoked responses in each of the auditory fields tested. The neural response to consonants was significantly stronger in anterior auditory field (AAF) and A1 following speech training. The neural response to vowels following speech training was significantly weaker in ventral auditory field (VAF) and posterior auditory field (PAF). This differential plasticity of consonant and vowel sound responses may result from the greater paired pulse depression, expanded low frequency tuning, reduced frequency selectivity, and lower tone thresholds, which occurred across the four auditory fields. These findings suggest that alterations in the distributed processing of behaviorally relevant sounds may contribute to robust speech discrimination. PMID:25827927

  19. Hemodynamic responses in human multisensory and auditory association cortex to purely visual stimulation

    PubMed Central

    Meyer, Martin; Baumann, Simon; Marchina, Sarah; Jancke, Lutz

    2007-01-01

    Background Recent findings of a tight coupling between visual and auditory association cortices during multisensory perception in monkeys and humans raise the question whether consistent paired presentation of simple visual and auditory stimuli prompts conditioned responses in unimodal auditory regions or multimodal association cortex once visual stimuli are presented in isolation in a post-conditioning run. To address this issue fifteen healthy participants partook in a "silent" sparse temporal event-related fMRI study. In the first (visual control) habituation phase they were presented with briefly red flashing visual stimuli. In the second (auditory control) habituation phase they heard brief telephone ringing. In the third (conditioning) phase we coincidently presented the visual stimulus (CS) paired with the auditory stimulus (UCS). In the fourth phase participants either viewed flashes paired with the auditory stimulus (maintenance, CS-) or viewed the visual stimulus in isolation (extinction, CS+) according to a 5:10 partial reinforcement schedule. The participants had no other task than attending to the stimuli and indicating the end of each trial by pressing a button. Results During unpaired visual presentations (preceding and following the paired presentation) we observed significant brain responses beyond primary visual cortex in the bilateral posterior auditory association cortex (planum temporale, planum parietale) and in the right superior temporal sulcus whereas the primary auditory regions were not involved. By contrast, the activity in auditory core regions was markedly larger when participants were presented with auditory stimuli. Conclusion These results demonstrate involvement of multisensory and auditory association areas in perception of unimodal visual stimulation which may reflect the instantaneous forming of multisensory associations and cannot be attributed to sensation of an auditory event. More importantly, we are able to show that brain

  20. Is There More than One Steady State for Nox?

    NASA Technical Reports Server (NTRS)

    Bakas, G.

    1985-01-01

    The study of alternative steady states for nitrogen oxides is discussed: The production of these oxides and the reactions they undergo in the atmosphere are described. The computerized modelling of the atmosphere using a one dimensional time dependent photochemical model is attempted.

  1. Effects of curvature on asymmetric steady states in catalyst particles

    SciTech Connect

    Lucier, B J

    1981-02-01

    The effects of curvature on steady states of chemical catalytic reactions are investigated by studying the cases of the catalytic particle being a spherical or cylindrical shell. Existence and stability of solutions are studied. It is shown that the solutions converge to the solutions for the catalytic slab when the curvature goes to 0 in each case.

  2. Equilibrium Binding and Steady-State Enzyme Kinetics.

    ERIC Educational Resources Information Center

    Dunford, H. Brian

    1984-01-01

    Points out that equilibrium binding and steady-state enzyme kinetics have a great deal in common and that related equations and error analysis can be cast in identical forms. Emphasizes that if one type of problem solution is taught, the other is also taught. Various methods of data analysis are evaluated. (JM)

  3. Steady-State Multiplicity Features of Chemically Reacting Systems.

    ERIC Educational Resources Information Center

    Luss, Dan

    1986-01-01

    Analyzes steady-state multiplicity in chemical reactors, focusing on the use of two mathematical tools, namely, the catastrophe theory and the singularity theory with a distinguished parameter. These tools can be used to determine the maximum number of possible solutions and the different types of bifurcation diagrams. (JN)

  4. Steady State Load Characterization Fact Sheet: 2012 Chevy Volt

    SciTech Connect

    Don Scoffield

    2015-01-01

    This fact sheet characterizes the steady state charging behavior of a 2012 Chevy Volt. Both level 1 charging (120 volt) and level 2 charging (208 volts) is investigated. This fact sheet contains plots of efficiency, power factor, and current harmonics as vehicle charging is curtailed. Prominent current harmonics are also displayed in a histogram for various charge rates.

  5. CONTROL OF CRYPTOSPORIDIUM OOCYSTS BY STEADY-STATE CONVENTIONAL TREATMENT

    EPA Science Inventory

    Pilot-scale experiments have been performed to assess the ability of conventional treatment to control Cryptosporidium oocysts under steady-state conditions. The work was performed with a pilot plant that was designed to minimize flow rates and, as a result, the number of oocyst...

  6. Pressure updating methods for the steady-state fluid equations

    NASA Technical Reports Server (NTRS)

    Fiterman, A.; Turkel, E.; Vatsa, V.

    1995-01-01

    We consider the steady state equations for a compressible fluid. Since we wish to solve for a range of speeds we must consider the equations in conservation form. For transonic speeds these equations are of mixed type. Hence, the usual approach is to add time derivatives to the steady state equations and then march these equations in time. One then adds a time derivative of the density to the continuity equation, a derivative of the momentum to the momentum equation and a derivative of the total energy to the energy equation. This choice is dictated by the time consistent equations. However, since we are only interested in the steady state this is not necessary. Thus we shall consider the possibility of adding a time derivative of the pressure to the continuity equation and similar modifications for the energy equation. This can then be generalized to adding combinations of time derivatives to each equation since these vanish in the steady state. When using acceleration techniques such as residual smoothing, multigrid, etc. these are applied to the pressure rather than the density. Hence, the code duplicates the behavior of the incompressible equations for low speeds.

  7. The Development of Strategies for the Steady State.

    ERIC Educational Resources Information Center

    Wolfman, Brunetta R.; Wolfman, Burton

    1980-01-01

    Presented is a matrix of institution types and institutional characteristics that can be used in planning for the steady state in colleges and universities. Case studies of six institutions are presented: Harvard University, Boston University, Dartmouth College, Colorado College, University of Massachusetts/Boston, and Massachusetts Community…

  8. Steady-State Pharmacokinetics of Bupropion SR in Juvenile Patients

    ERIC Educational Resources Information Center

    Daviss, W. Burleson; Perel, James M.; Rudolph, George R.; Axelson, David A.; Gilchrist, Richard; Nuss, Sharon; Birmaher, Boris; Brent, David A.

    2005-01-01

    Objective: To examine the steady-state pharmacokinetic properties of bupropion sustained release (SR) and their potential developmental differences in youths. Method: Eleven boys and eight girls aged 11 to 17 years old were prescribed bupropion SR monotherapy for attention-deficit/hyperactivity disorder (n = 16) and/or depressive disorders (n =…

  9. Density Functional Theory for Steady-State Nonequilibrium Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Liu, Shuanglong; Nurbawono, Argo; Zhang, Chun

    2015-10-01

    We present a density functional theory (DFT) for steady-state nonequilibrium quantum systems such as molecular junctions under a finite bias. Based on the steady-state nonequilibrium statistics that maps nonequilibrium to an effective equilibrium, we show that ground-state DFT (GS-DFT) is not applicable in this case and two densities, the total electron density and the density of current-carrying electrons, are needed to uniquely determine the properties of the corresponding nonequilibrium system. A self-consistent mean-field approach based on two densities is then derived. The theory is implemented into SIESTA computational package and applied to study nonequilibrium electronic/transport properties of a realistic carbon-nanotube (CNT)/Benzene junction. Results obtained from our steady-state DFT (SS-DFT) are compared with those of conventional GS-DFT based transport calculations. We show that SS-DFT yields energetically more stable nonequilibrium steady state, predicts significantly lower electric current, and is able to produce correct electronic structures in local equilibrium under a limiting case.

  10. Combined Steady-State and Dynamic Heat Exchanger Experiment

    ERIC Educational Resources Information Center

    Luyben, William L.; Tuzla, Kemal; Bader, Paul N.

    2009-01-01

    This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…