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Sample records for hz steady-state response

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  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. 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

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. 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

  14. 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

  15. [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

  16. Steady-state and dynamic characteristics of a 20-kHz spacecraft power system - Control of harmonic resonance

    NASA Technical Reports Server (NTRS)

    Wasynczuk, O.; Krause, P. C.; Biess, J. J.; Kapustka, R.

    1990-01-01

    A detailed computer simulation was used to illustrate the steady-state and dynamic operating characteristics of a 20-kHz resonant spacecraft power system. The simulated system consists of a parallel-connected set of DC-inductor resonant inverters (drivers), a 440-V cable, a node transformer, a 220-V cable, and a transformer-rectifier-filter (TRF) AC-to-DC receiver load. Also included in the system are a 1-kW 0.8-pf RL load and a double-LC filter connected at the receiving end of the 20-kHz AC system. The detailed computer simulation was used to illustrate the normal steady-state operating characteristics and the dynamic system performance following, for example, TRF startup. It is shown that without any filtering the given system exhibits harmonic resonances due to an interaction between the switching of the source and/or load converters and the AC system. However, the double-LC filter at the receiving-end of the AC system and harmonic traps connected in series with each of the drivers significantly reduce the harmonic distortion of the 20-kHz bus voltage. Significant additional improvement in the waveform quality can be achieved by including a double-LC filter with each driver.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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 ...

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. [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

  2. 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

  3. 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

  4. 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.

  5. 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)

  6. 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.

  7. 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.

  8. 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.

  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. Cardiovascular response of rats exposed to 60-Hz electric fields

    SciTech Connect

    Hilton, D.I.; Phillips, R.D.

    1980-01-01

    Recently, it has been reported that exposure to high-strength electric fields can influence electrocardiogram (ECG) patterns, heart rates, and blood pressures in various species of animals. Our studies were designed to evaluate these reported effects and to help clarify some of the disagreement present in the literature. Various cardiovascular variables were measured in Sprague-Dawley rats exposed or sham-exposed to 60-Hz electric fields at 80 to 100 kV/m for periods up to four months. No significant differences in heart rates, ECG patterns, blood pressures, or vascular reactivity were observed between exposed and sham-exposed rats after 8 hours, 40 hours, 1 month, or 4 months of exposure. Our studies cannot be directly compared to the work of other investigators because of differences in animal species and electric-field characteristics. However, our failure to detect any cardiovascular changes may have been the result of (1) eliminating secondary field effects such as shocks, audible noise, corona, and ozone; (2) minimizing steady-state microcurrents between the mouth of the animal and watering devices; and (3) minimizing electric-field-induced vibration of the electrodes and animal cages.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  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. [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

  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. 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

  2. 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

  3. Amplitude modulation of steady-state visual evoked potentials by event-related potentials in a working memory task

    PubMed Central

    Yao, Dezhong; Tang, Yu; Huang, Yilan; Su, Sheng

    2009-01-01

    Previous studies have shown that the amplitude and phase of the steady-state visual-evoked potential (SSVEP) can be influenced by a cognitive task, yet the mechanism of this influence has not been understood. As the event-related potential (ERP) is the direct neural electric response to a cognitive task, studying the relationship between the SSVEP and ERP would be meaningful in understanding this underlying mechanism. In this work, the traditional average method was applied to extract the ERP directly, following the stimulus of a working memory task, while a technique named steady-state probe topography was utilized to estimate the SSVEP under the simultaneous stimulus of an 8.3-Hz flicker and a working memory task; a comparison between the ERP and SSVEP was completed. The results show that the ERP can modulate the SSVEP amplitude, and for regions where both SSVEP and ERP are strong, the modulation depth is large. PMID:19960240

  4. High-frequency combination coding-based steady-state visual evoked potential for brain computer interface

    SciTech Connect

    Zhang, Feng; Zhang, Xin; Xie, Jun; Li, Yeping; Han, Chengcheng; Lili, Li; Wang, Jing; Xu, Guang-Hua

    2015-03-10

    This study presents a new steady-state visual evoked potential (SSVEP) paradigm for brain computer interface (BCI) systems. The goal of this study is to increase the number of targets using fewer stimulation high frequencies, with diminishing subject’s fatigue and reducing the risk of photosensitive epileptic seizures. The new paradigm is High-Frequency Combination Coding-Based High-Frequency Steady-State Visual Evoked Potential (HFCC-SSVEP).Firstly, we studied SSVEP high frequency(beyond 25 Hz)response of SSVEP, whose paradigm is presented on the LED. The SNR (Signal to Noise Ratio) of high frequency(beyond 40 Hz) response is very low, which is been unable to be distinguished through the traditional analysis method; Secondly we investigated the HFCC-SSVEP response (beyond 25 Hz) for 3 frequencies (25Hz, 33.33Hz, and 40Hz), HFCC-SSVEP produces n{sup n} with n high stimulation frequencies through Frequence Combination Code. Further, Animproved Hilbert-huang transform (IHHT)-based variable frequency EEG feature extraction method and a local spectrum extreme target identification algorithmare adopted to extract time-frequency feature of the proposed HFCC-SSVEP response.Linear predictions and fixed sifting (iterating) 10 time is used to overcome the shortage of end effect and stopping criterion,generalized zero-crossing (GZC) is used to compute the instantaneous frequency of the proposed SSVEP respondent signals, the improved HHT-based feature extraction method for the proposed SSVEP paradigm in this study increases recognition efficiency, so as to improve ITR and to increase the stability of the BCI system. what is more, SSVEPs evoked by high-frequency stimuli (beyond 25Hz) minimally diminish subject’s fatigue and prevent safety hazards linked to photo-induced epileptic seizures, So as to ensure the system efficiency and undamaging.This study tests three subjects in order to verify the feasibility of the proposed method.

  5. 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.

  6. 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)

  7. 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.

  8. 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.

  9. 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)

  10. 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).

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Steady-state plasma transition in the Venus ionosheath

    NASA Technical Reports Server (NTRS)

    Perez-De-tejada, H.; Intriligator, D. S.; Strangeway, R. J.

    1991-01-01

    The results of an extended analysis of the plasma and electric field data of the Pioneer Venus Orbiter (PVO) are presented. The persistent presence of a plasma transition embedded in the flanks of the Venus ionosheath between the bow shock and the ionopause is reported. This transition is identified by the repeated presence of characteristic bursts in the 30 kHz channel of the electric field detector of the PVO. The observed electric field signals coincide with the onset of different plasma conditions in the inner ionosheath where more rarified plasma fluxes are measured. The repeated identification of this intermediate ionosheath transition in the PVO data indicates that it is present as a steady state feature of the Venus plasma environment. The distribution of PVO orbits in which the transition is observed suggests that it is more favorably detected in the vicinity of and downstream from the terminator.

  4. 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.

  5. 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.

  6. 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.

  7. 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...

  8. 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)

  9. 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.

  10. The auditory transient 40-Hz response is insensitive to changes in stimulus features.

    PubMed

    Tiitinen, H; Sinkkonen, J; May, P; Näätänen, R

    1994-12-30

    Ten subjects were presented with tone pips occasionally interspersed with deviant tone pips of a higher frequency. The transient 40-Hz response was insensitive to change in qualitative stimulus features. In contrast, stimulus changes elicited a later and slower event-related potential, the mismatch negativity (MMN). As a response to changes in stimulus features implies the existence of a memory system, and because changes in qualitative stimulus aspects do not activate the generator mechanisms underlying the 40-Hz response, the 40-Hz response can be dissociated from memory mechanisms. Furthermore, the analysis of phase-locked (synchronous) and non-phase-locked (asynchronous) responses revealed that the 40-Hz response might be caused by the synchronization of already active oscillators. PMID:7703412

  11. Steady-state evoked potentials to tag specific components of nociceptive cortical processing.

    PubMed

    Colon, Elisabeth; Nozaradan, Sylvie; Legrain, Valery; Mouraux, André

    2012-03-01

    Studies have shown that the periodic repetition of a stimulus induces, at certain stimulation frequencies, a sustained electro-cortical response of corresponding frequency, referred to as steady-state evoked potential (SSEP). Using infrared laser stimulation, we recently showed that SSEPs can be used to explore nociceptive cortical processing. Here, we implemented a novel approach to elicit such responses, using a periodic intra-epidermal electrical stimulation of cutaneous Aδ-nociceptors (Aδ-SSEPs). Using a wide range of frequencies (3-43 Hz), we compared the scalp topographies and temporal dynamics of these Aδ-SSEPs to the Aβ-SSEPs elicited by non-nociceptive transcutaneous electrical stimulation, as well as to the transient ERPs elicited by the onsets of the 10-s stimulation trains, applied to the left and right hand. At 3 Hz, we found that the topographies of Aβ- and Aδ-SSEPs were both maximal at the scalp vertex, and resembled closely that of the late P2 wave of transient ERPs, suggesting activity originating from the same neuronal populations. The responses also showed marked habituation, suggesting that they were mainly related to unspecific, attention-related processes. In contrast, at frequencies >3 Hz, the topographies of Aβ- and Aδ-SSEPs were markedly different. Aβ-SSEPs were maximal over the contralateral parietal region, whereas Aδ-SSEPs were maximal over midline frontal regions, thus indicating an entrainment of distinct neuronal populations. Furthermore, the responses showed no habituation, suggesting more obligatory and specific stages of sensory processing. Taken together, our results indicate that Aβ- and Aδ-SSEPs offer a unique opportunity to study the cortical representation of nociception and touch. PMID:22197788

  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. 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

  1. 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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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.

  9. 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.

  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. Revised Model of the Steady-state Solar Wind Halo Electron Velocity Distribution Function

    NASA Astrophysics Data System (ADS)

    Yoon, Peter H.; Kim, Sunjung; Choe, G. S.; moon, Y.-J.

    2016-08-01

    A recent study discussed the steady-state model for solar wind electrons during quiet time conditions. The electrons emanating from the Sun are treated in a composite three-population model—the low-energy Maxwellian core with an energy range of tens of eV, the intermediate ˜102–103 eV energy-range (“halo”) electrons, and the high ˜103–105 eV energy-range (“super-halo”) electrons. In the model, the intermediate energy halo electrons are assumed to be in resonance with transverse EM fluctuations in the whistler frequency range (˜102 Hz), while the high-energy super-halo electrons are presumed to be in steady-state wave–particle resonance with higher-frequency electrostatic fluctuations in the Langmuir frequency range (˜105 Hz). A comparison with STEREO and WIND spacecraft data was also made. However, ignoring the influence of Langmuir fluctuations on the halo population turns out to be an unjustifiable assumption. The present paper rectifies the previous approach by including both Langmuir and whistler fluctuations in the construction of the steady-state velocity distribution function for the halo population, and demonstrates that the role of whistler-range fluctuation is minimal unless the fluctuation intensity is arbitrarily raised. This implies that the Langmuir-range fluctuations, known as the quasi thermal noise, are important for both halo and super-halo electron velocity distribution.

  12. Revised Model of the Steady-state Solar Wind Halo Electron Velocity Distribution Function

    NASA Astrophysics Data System (ADS)

    Yoon, Peter H.; Kim, Sunjung; Choe, G. S.; moon, Y.-J.

    2016-08-01

    A recent study discussed the steady-state model for solar wind electrons during quiet time conditions. The electrons emanating from the Sun are treated in a composite three-population model—the low-energy Maxwellian core with an energy range of tens of eV, the intermediate ∼102–103 eV energy-range (“halo”) electrons, and the high ∼103–105 eV energy-range (“super-halo”) electrons. In the model, the intermediate energy halo electrons are assumed to be in resonance with transverse EM fluctuations in the whistler frequency range (∼102 Hz), while the high-energy super-halo electrons are presumed to be in steady-state wave–particle resonance with higher-frequency electrostatic fluctuations in the Langmuir frequency range (∼105 Hz). A comparison with STEREO and WIND spacecraft data was also made. However, ignoring the influence of Langmuir fluctuations on the halo population turns out to be an unjustifiable assumption. The present paper rectifies the previous approach by including both Langmuir and whistler fluctuations in the construction of the steady-state velocity distribution function for the halo population, and demonstrates that the role of whistler-range fluctuation is minimal unless the fluctuation intensity is arbitrarily raised. This implies that the Langmuir-range fluctuations, known as the quasi thermal noise, are important for both halo and super-halo electron velocity distribution.

  13. 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

  14. 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)

  15. 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.

  16. 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.

  17. 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.…

  18. 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...

  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. 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.

  2. Orbit response matrix measurements for 10Hz global orbit feedback in RHIC

    SciTech Connect

    Liu, C.; Minty, M.

    2010-10-01

    The 10 Hz global orbit feedback system (gofb) was designed to correct the 10 Hz horizontal beam perturbations in both rings that are suspected to be caused by vibrations of the final focusing quadrupoles (triplets). The full system envisioned for Run-11 consists of 36 BPMs, corresponding to 2 per triplet in each of the 12 triplet locations and two in each of the 6 arcs, and 1 dipole corrector at each triplet location for a total of 12 correctors. Prototype testing was successfully carried out during RHIC Run-10 in store condition with 4 new dipole correctors (with independent power supplies) and 8 stripline beam position monitors (BPMs) per accelerator. An SVD-based algorithm was used to compute the applied corrections. For Run-10, the response matrix was provided by W. W. MacKay. The response matrix R relates corrector angles to beam displacements at BPMs.

  3. New steady-state quiescent high-confinement plasma in an experimental advanced superconducting tokamak.

    PubMed

    Hu, J S; Sun, Z; Guo, H Y; Li, J G; Wan, B N; Wang, H Q; Ding, S Y; Xu, G S; Liang, Y F; Mansfield, D K; Maingi, R; Zou, X L; Wang, L; Ren, J; Zuo, G Z; Zhang, L; Duan, Y M; Shi, T H; Hu, L Q

    2015-02-01

    A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development. PMID:25699449

  4. Relative intelligibility of dynamically extracted transient versus steady-state components of speech

    NASA Astrophysics Data System (ADS)

    Boston, J. R.; Yoo, Sungyub; Li, C. C.; El-Jaroudi, Amro; Durrant, J. D.; Kovacyk, Kristie; Karn, Stacey

    2001-05-01

    Consonants are recognized to dominate higher frequencies of the speech spectrum and to carry more information than vowels, but both demonstrate quasi-steady state and transient components, such as vowel to consonant transitions. Fixed filters somewhat separate these effects, but probably not optimally, given diverse words, speakers, and situations. To enhance the transient characteristics of speech, this study used time-varying adaptive filters [Rao and Kumaresan, IEEE Trans. Speech Audio Process. 8, 240-254 (2000)], following high-pass filtering at 700 Hz (well-known to have minimal effect on intelligibility), to extract predominantly steady-state components of speech material (CVC words, NU-6). The transient component was the difference between the sum of the filter outputs and the original signal. Psychometric functions were determined in five subjects with and without background noise and fitted by ogives. The transient components averaged filtered speech energy, but PBmax was not significantly different (nonparametric ANOVA) from that of either the original or highpass filtered speech. The steady-state components yielded significantly lower PBmax (p 3D 0.003) despite their much greater energy, as expected. These results suggest a potential approach to dynamic enhancement of speech intelligibility. [Work supported by ONR.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. Central resetting of neuromuscular steady states may underlie rhythmical arm movements.

    PubMed

    Ustinova, Ksenia I; Feldman, Anatol G; Levin, Mindy F

    2006-09-01

    Changing the steady-state configuration of the body or its segments may be an important function of central pattern generators for locomotion and other rhythmical movements. Thereby, muscle activation, forces, and movement may emerge following a natural tendency of the neuromuscular system to achieve the current steady-state configuration. To verify that transitions between different steady states occur during rhythmical movements, we asked standing subjects to swing one or both arms synchronously or reciprocally at approximately 0.8 Hz from the shoulder joints. In randomly selected cycles, one arm was transiently arrested by an electromagnetic device. Swinging resumed after some delay and phase resetting. During bilateral swinging, the nonperturbed arm often stopped before resuming swinging at a position that was close to either the extreme forward or the extreme backward arm position observed before the perturbation. Oscillations usually resumed when both arms arrived at similar extreme positions when a synchronous bilateral pattern was initially produced or at the opposite positions if the initial pattern was reciprocal. Results suggest that a central generator controls both arms as a coherent unit by producing transitions between its steady state (equilibrium) positions. By controlling these positions, the system may define the spatial boundaries of movement. At these positions, the system may halt the oscillations, resume them at a new phase (as observed in the present study), or initiate a new motor action. Our findings are relevant to locomotion and suggest that walking may also be generated by transitions between several equilibrium configurations of the body, possibly accomplished by modulation and gating of proprioceptive reflexes. PMID:16707712

  14. Steady-State Pursuit Is Driven by Object Motion Rather Than the Vector Average of Local Motions

    NASA Technical Reports Server (NTRS)

    Stone, Leland S.; Beutter, B. R.; Lorenceau, J. D.; Ahumada, Al (Technical Monitor)

    1997-01-01

    We have previously shown that humans can pursue the motion of objects whose trajectories can be recovered only by spatio-temporal integration of local motion signals. We now explore the integration rule used to derive the target-motion signal driving pursuit. We measured the pursuit response of 4 observers (2 naive) to the motion of a line-figure diamond viewed through two vertical bar apertures (0.2 cd/square m). The comers were always occluded so that only four line segments (93 cd/square m) were visible behind the occluding foreground (38 cd/square m). The diamond was flattened (40 & 140 degree vertex angles) such that vector averaging of the local normal motions and vertical integration (e.g. IOC) yield very I or different predictions, analogous to using a Type II plaid. The diamond moved along Lissajous-figure trajectories (Ax = Ay = 2 degrees; TFx = 0.8 Hz; TFy = 0.4 Hz). We presented only 1.25 cycles and used 6 different randomly interleaved initial relative phases to minimize the role of predictive strategies. Observers were instructed to track the diamond and reported that its motion was always coherent (unlike type II plaids). Saccade-free portions of the horizontal and vertical eye-position traces sampled at 240 Hz were fit by separate sinusoids. Pursuit gain with respect to the diamond averaged 0.7 across subjects and directions. The ratio of the mean vertical to horizontal amplitude of the pursuit response was 1.7 +/- 0.7 averaged across subjects (1SD). This is close to the prediction of 1.0 from vertical motion-integration rules, but far from 7.7 predicted by vector averaging and infinity predicted by segment- or terminator-tracking strategies. Because there is no retinal motion which directly corresponds to the diamond's motion, steady-state pursuit of our "virtual" diamond is not closed-loop in the traditional sense. Thus, accurate pursuit is unlikely to result simply from local retinal negative feedback. We conclude that the signal driving steady-state

  15. 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.

  16. 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.

  17. 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)

  18. 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)

  19. 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.

  20. 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...

  1. 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.

  2. 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…

  3. 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 =…

  4. 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.

  5. 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…

  6. Steady-State Squeezing in the Micromaser Cavity Field

    NASA Technical Reports Server (NTRS)

    Nayak, N.

    1996-01-01

    It is shown that the radiation field in the presently operated micromaser cavity may be squeezed when pumped with polarized atoms. The squeezing is in the steady state field corresponding to the action similar to that of the conventional micromaser, with the effect of cavity dissipation during entire t(sub c) = tau + t(sub cav).

  7. Steady States of the Parametric Rotator and Pendulum

    ERIC Educational Resources Information Center

    Bouzas, Antonio O.

    2010-01-01

    We discuss several steady-state rotation and oscillation modes of the planar parametric rotator and pendulum with damping. We consider a general elliptic trajectory of the suspension point for both rotator and pendulum, for the latter at an arbitrary angle with gravity, with linear and circular trajectories as particular cases. We treat the…

  8. Experimental study of multiple steady states in homogeneous azeotropic distillation

    SciTech Connect

    Guettinger, T.E.; Dorn, C.; Morari, M.

    1997-03-01

    Bekiaris et al. (1993) explained the existence of multiple steady states in homogeneous ternary azeotropic distillation, on the basis of the analysis of the case of infinite reflux and infinite column length (infinite number of trays). They showed that the predictions of multiple steady states for such infinite columns have relevant implications for columns of finite length operated at finite reflux. In this article, experiments are described for the ternary homogeneous system methanol-methyl butyrate-toluene which demonstrate the existence of multiple steady states (output multiplicities) caused by the vapor-liquid-equilibrium. The experiments on an industrial pilot column show two stable steady states for the same feed flow rate and composition and the same set of operating parameters. The measurements are in excellent agreement with the predictions obtained for infinite columns using the {infinity}/{infinity} analysis tool as well as with stage-by-stage simulation results. These experiments represent the first published study reporting evidence for the predictions and simulations by various researchers showing that type of output multiplicities in distillation.

  9. Steady-State Dynamic Behavior of a Flexible Rotor With Auxiliary Support From a Clearance Bearing

    NASA Technical Reports Server (NTRS)

    Xie, Huajun; Flowers, George T.; Feng, Li; Lawrence, Charles T.

    1996-01-01

    This paper investigates the steady-state responses of a rotor system supported by auxiliary bearings in which there is a clearance between the rotor and the inner race of the bearing. A simulation model based upon the rotor of a production jet engine is developed and its steady-state behavior is explored over a wide range of operating conditions for various parametric configurations. Specifically, the influence of rotor imbalance, clearance, support stiffness and damping is studied. Bifurcation diagrams are used as a tool to examine the dynamic behavior of this system as a function of the afore mentioned parameters. The harmonic balance method is also employed for synchronous response cases. The observed dynamical responses is discussed and some insights into the behavior of such systems are presented.

  10. Steady state growth of E. Coli in low ammonium environment

    NASA Astrophysics Data System (ADS)

    Kim, Minsu; Deris, Barret; Zhang, Zhongge; Hwa, Terry

    2011-03-01

    Ammonium is the preferred nitrogen source for many microorganisms. In medium with low ammonium concentrations, enteric bacteria turn on the nitrogen responsive (ntr) genes to assimilate ammonium. Two proteins in E. coli, Glutamine synthetase (GS) and the Ammonium/methylammonium transporter AmtB play crucial roles in this regard. GS is the major ammonium assimilation enzyme below 1mM of NH4 + . AmtB is an inner membrane protein that transports NH4 + across the cell membrane against a concentration gradient. In order to study ammonium uptake at low NH4 + concentration at neutral pH, we developed a microfluidic flow chamber that maintains a homogenous nutrient environment during the course of exponential cell growth, even at very low concentration of nutrients. Cell growth can be accurately monitored using time-lapse microscopy. We followed steady state growth down to micro-molar range of NH4 + for the wild type and Δ amtB strains. The wild type strain is able to maintain the growth rate from 10mM down to a few uM of NH4 + , while the mutant exhibited reduced growth below ~ 20 ~uM of NH4 + . Simultaneous characterization of the expression levels of GS and AmtB using fluorescence reporters reveals that AmtB is turned on already at 1mM, but contributes to function only below ~ 30 ~uM in the wild-type. Down to ~ 20 ~uM of NH4 + , E.~coli can compensate the loss of AmtB by GS alone.

  11. Retinoic acid inhibits the cytoproliferative response to weak 50-Hz magnetic fields in neuroblastoma cells

    PubMed Central

    TRILLO, MARÍA ÁNGELES; MARTÍNEZ, MARÍA ANTONIA; CID, MARÍA ANTONIA; ÚBEDA, ALEJANDRO

    2012-01-01

    We previously reported that intermittent exposure to a 50-Hz magnetic field (MF) at 100 μT stimulates cell proliferation in the human neuroblastoma cell line NB69. The present study aimed to investigate whether the magnetic field-induced growth promotion also occurs at a lower magnetic flux density of 10 μT. To this purpose, NB69 cells were subjected for 42 h to intermittent exposure, 3 h on/3 h off, to a 50-Hz MF at a 10 or 100 μT magnetic flux density. The field exposure took place either in the presence or in the absence of the antiproliferative agent retinoic acid. At the end of the treatment and/or incubation period, the cell growth was estimated by hemocytometric counting and spectrophotometric analysis of total protein and DNA contents. Potential changes in DNA synthesis were also assessed through proliferating cell nuclear antigen (PCNA) immunolabeling. The results confirmed previously reported data that a 42-h exposure to a 50-Hz sine wave MF at 100 μT promotes cell growth in the NB69 cell line, and showed that 10 μT induces a similar proliferative response. This effect, which was significantly associated and linearly correlated with PCNA expression, was abolished by the presence of retinoic acid in the culture medium. PMID:23292364

  12. Hemodynamic responses can modulate the brain oscillations in low frequency

    NASA Astrophysics Data System (ADS)

    Lu, Feng-Mei; Wang, Yi-Feng; Yuan, Zhen

    2016-03-01

    Previous studies have showed that the steady-state responses were able to be used as an effective index for modulating the neural oscillations in the high frequency ranges (> 1 Hz). However, the neural oscillations in low frequency ranges (<1 Hz) remain unknown. In this study, a series of fNIRS experimental tests were conducted to validate if the low frequency bands (0.1 Hz - 0.8 Hz) steady-state hemoglobin responses (SSHbRs) could be evoked and modulate the neural oscillation during a serial reaction time (SRT) task.

  13. 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

  14. Steady state volcanism: Evidence from eruption histories of polygenetic volcanoes

    SciTech Connect

    Wadge, G.

    1982-05-10

    Some volcanoes erupt magma at average rates which are constant over periods of many years, even through this magma may appear in a complex series of eruptions. This constancy of output is tested by construction of a curve of cumulative volume of erupted magma, which is linear for steady state volcanism, and whose gradient defines the steady state rate Q/sub s/s. The assumption is made that Q/sub s/s is the rate at which magma is supplied to these polygenetic volcanoes. Five general types of eruptive behavior can be distinguished from the cumulative volume studied. These types are interpreted in terms of a simple model of batches of magma rising buoyantly through the crust and interacting with a small-capacity subvolcanic magma reservoir. Recognition of previous steady state behavior at a volcano may enable the cumulative volume curve to be used empirically as a constraint on the timing and volume of the next eruption. The steady state model thus has a limited predictive capability. With the exception of Kilauea (O/sub s/s = 4m/sup 3/ s/sup -1/) all the identified steady state volcanoes have values of Q/sub s/s of a few tenths of one cubic meter per second. These rates are consistent with the minimum flux rates required by theoretical cooling models of batches of magma traversing the crust. The similarity of these Q/sub s/s values of volcanoes (producing basalt, andesite, and dacite magmas) in very different tectonic settings suggests that the common factors of crustal buoyancy forces and the geotherm-controlled cooling rates control the dynamics of magma supply through the crust. Long-term dormancy at active volcanoes may be a manifestation of the steady accumulation of magma in large crustal reservoirs, a process that complements the intermittent periods of steady state output at the surface. This possibility has several implications, the most important of which is that it provides a constraint on the supply rate of new magma to the bases of plutons.

  15. Steady-state spin squeezing generation in diamond nanostructures

    NASA Astrophysics Data System (ADS)

    Ma, Yong-Hong; Zhang, Xue-Feng

    2014-04-01

    As one kind of many body entangled states, spin squeezed states can be used to implement the high precise measurement beyond the standard quantum limit. Inspired by the novel spin squeezing scheme based on phonon-induced spin-spin interactions [S. D. Bennett et al., Phys. Rev. Lett. 110, 156402 (2013), 10.1103/PhysRevLett.110.156402], we reexamine the steady-state behaviors for the spin ensemble in diamond nanostructures by exerting a controllable microwave field. By using the phase-space approach we calculate analytically fluctuations of collective spin operators. We find that there is bistability and spin squeezing for the steady-state spin ensemble, despite the mechanical damping considered. Moreover, our work shows that bistability and spin squeezing can be controlled by microwave field and Zeeman splitting. The present scheme can be used to increase the stability of spin clocks, magnetometers, and other measurements based on spin-spin interaction in diamond nanostructures.

  16. Turnover of messenger RNA: Polysome statistics beyond the steady state

    NASA Astrophysics Data System (ADS)

    Valleriani, A.; Ignatova, Z.; Nagar, A.; Lipowsky, R.

    2010-03-01

    The interplay between turnover or degradation and ribosome loading of messenger RNA (mRNA) is studied theoretically using a stochastic model that is motivated by recent experimental results. Random mRNA degradation affects the statistics of polysomes, i.e., the statistics of the number of ribosomes per mRNA as extracted from cells. Since ribosome loading of newly created mRNA chains requires some time to reach steady state, a fraction of the extracted mRNA/ribosome complexes does not represent steady state conditions. As a consequence, the mean ribosome density obtained from the extracted complexes is found to be inversely proportional to the mRNA length. On the other hand, the ribosome density profile shows an exponential decrease along the mRNA for prokaryotes and becomes uniform in eukaryotic cells.

  17. Persistent Probability Currents in Non-equilibrium Steady States

    NASA Astrophysics Data System (ADS)

    Zia, Royce; Mellor, Andrew; Mobilia, Mauro; Fox-Kemper, Baylor; Weiss, Jeffrey

    For many interesting phenomena in nature, from all life forms to the global climate, the fundamental hypothesis of equilibrium statistical mechanics does not apply. Instead, they are perhaps better characterized by non-equilibrium steady states, evolving with dynamical rules which violate detailed balance. In particular, such dynamics leads to the existence of non-trivial, persistent probability currents - a principal characteristic of non-equilibrium steady states. In turn, they give rise to the notion of 'probability angular momentum'. Observable manifestations of such abstract concepts will be illustrated in two distinct contexts: a heterogeneous nonlinear voter model and our ocean heat content. Supported in part by grants from the Bloom Agency (Leeds, UK) and the US National Science Foundation: OCE-1245944. AM acknowledges the support of EPSRC Industrial CASE Studentship, Grant No. EP/L50550X/1.

  18. Nonequilibrium Steady States of a Stochastic Model System.

    NASA Astrophysics Data System (ADS)

    Zhang, Qiwei

    We study the nonequilibrium steady state of a stochastic lattice gas model, originally proposed by Katz, Lebowitz and Spohn (Phys. Rev. B 28: 1655 (1983)). Firstly, we solve the model on some small lattices exactly in order to see the general dependence of the steady state upon different parameters of the model. Nextly, we derive some analytical results for infinite lattice systems by taking some suitable limits. We then present some renormalization group results for the continuum version of the model via field theoretical techniques, the supersymmetry of the critical dynamics in zero field is also explored. Finally, we report some very recent 3-D Monte Carlo simulation results, which have been obtained by applying Multi-Spin-Coding techniques on a CDC vector supercomputer - Cyber 205 at John von Neumann Center.

  19. Hydrodynamics of stratified epithelium: Steady state and linearized dynamics

    NASA Astrophysics Data System (ADS)

    Yeh, Wei-Ting; Chen, Hsuan-Yi

    2016-05-01

    A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.

  20. Steady States in Fermionic Interacting Dissipative Floquet Systems

    NASA Astrophysics Data System (ADS)

    Seetharam, Karthik; Bardyn, Charles; Lindner, Netanel; Rudner, Mark; Refael, Gil

    The possibility to drive quantum systems periodically in time offers unique ways to deeply modify their fundamental properties, as exemplified by Floquet topological insulators. It also opens the door to a variety of non-equilibrium effects. Resonant driving fields, in particular, lead to excitations which can expose the system to heating. We previously demonstrated that the analog of thermal states can be achieved and controlled in a fermionic Floquet system in the presence of phonon scattering, spontaneous emission, and an energy filtered fermionic bath. However, interactions play an important role in thermalization and present additional sources of heating. We analyze the effects of weak interactions in the presence of dissipation and the role of coherences in determining the steady state of the driven system. Interactions generically create additional excitations and, in contrast to phonons, may sustain inter-Floquet-band coherences at steady state.

  1. Steady-state current transfer and scattering theory.

    PubMed

    Ben-Moshe, Vered; Rai, Dhurba; Skourtis, Spiros S; Nitzan, Abraham

    2010-08-01

    The correspondence between the steady-state theory of current transfer and scattering theory in a system of coupled tight-binding models of one-dimensional wires is explored. For weak interwire coupling both calculations give nearly identical results, except at singular points associated with band edges. The effect of decoherence in each of these models is studied using a generalization of the Liouville-von Neuman equation suitable for steady-state situations. An example of a single impurity model is studied in detail, leading to a lattice model of scattering off target that affects both potential scattering and decoherence. For an impurity level lying inside the energy band, the transmission coefficient diminishes with increasing dephasing rate, while the opposite holds for impurity energy outside the band. The efficiency of current transfer in the coupled wire system decreases with increasing dephasing. PMID:20707524

  2. Master equation based steady-state cluster perturbation theory

    NASA Astrophysics Data System (ADS)

    Nuss, Martin; Dorn, Gerhard; Dorda, Antonius; von der Linden, Wolfgang; Arrigoni, Enrico

    2015-09-01

    A simple and efficient approximation scheme to study electronic transport characteristics of strongly correlated nanodevices, molecular junctions, or heterostructures out of equilibrium is provided by steady-state cluster perturbation theory. In this work, we improve the starting point of this perturbative, nonequilibrium Green's function based method. Specifically, we employ an improved unperturbed (so-called reference) state ρ̂S, constructed as the steady state of a quantum master equation within the Born-Markov approximation. This resulting hybrid method inherits beneficial aspects of both the quantum master equation as well as the nonequilibrium Green's function technique. We benchmark this scheme on two experimentally relevant systems in the single-electron transistor regime: an electron-electron interaction based quantum diode and a triple quantum dot ring junction, which both feature negative differential conductance. The results of this method improve significantly with respect to the plain quantum master equation treatment at modest additional computational cost.

  3. Optimal Control of Transitions between Nonequilibrium Steady States

    PubMed Central

    Zulkowski, Patrick R.; Sivak, David A.; DeWeese, Michael R.

    2013-01-01

    Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines. PMID:24386112

  4. Steady state magnetic field configurations for the earth's magnetotail

    NASA Technical Reports Server (NTRS)

    Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.

    1989-01-01

    A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).

  5. Analytic Steady-State Accuracy of a Spacecraft Attitude Estimator

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis

    2000-01-01

    This paper extends Farrenkopf's analysis of a single-axis spacecraft attitude estimator using gyro and angle sensor data to include the angle output white noise of a rate-integrating gyro. Analytic expressions are derived for the steady-state pre-update and post-update angle and drift bias variances and for the state update equations. It is shown that only part of the state update resulting from the angle sensor measurement is propagated to future times.

  6. Transitional steady states of exchange dynamics between finite quantum systems.

    PubMed

    Jeon, Euijin; Yi, Juyeon; Kim, Yong Woon

    2016-08-01

    We examine energy and particle exchange between finite-sized quantum systems and find a new form of nonequilibrium state. The exchange rate undergoes stepwise evolution in time, and its magnitude and sign dramatically change according to system size differences. The origin lies in interference effects contributed by multiply scattered waves at system boundaries. Although such characteristics are utterly different from those of true steady state for infinite systems, Onsager's reciprocal relation remains universally valid. PMID:27627275

  7. Steady-state superradiance with alkaline-earth-metal atoms

    SciTech Connect

    Meiser, D.; Holland, M. J.

    2010-03-15

    Alkaline-earth-metal-like atoms with ultranarrow transitions open the door to a new regime of cavity quantum electrodynamics. That regime is characterized by a critical photon number that is many orders of magnitude smaller than what can be achieved in conventional systems. We show that it is possible to achieve superradiance in steady state with such systems. We discuss the basic underlying mechanisms as well as the key experimental requirements.

  8. Robust random number generation using steady-state emission of gain-switched laser diodes

    SciTech Connect

    Yuan, Z. L. Lucamarini, M.; Dynes, J. F.; Fröhlich, B.; Plews, A.; Shields, A. J.

    2014-06-30

    We demonstrate robust, high-speed random number generation using interference of the steady-state emission of guaranteed random phases, obtained through gain-switching a semiconductor laser diode. Steady-state emission tolerates large temporal pulse misalignments and therefore significantly improves the interference quality. Using an 8-bit digitizer followed by a finite-impulse-response unbiasing algorithm, we achieve random number generation rates of 8 and 20 Gb/s, for laser repetition rates of 1 and 2.5 GHz, respectively, with a ±20% tolerance in the interferometer differential delay. We also report a generation rate of 80 Gb/s using partially phase-correlated short pulses. In relation to the field of quantum key distribution, our results confirm the gain-switched laser diode as a suitable light source, capable of providing phase-randomized coherent pulses at a clock rate of up to 2.5 GHz.

  9. Cyclic steady state stress-strain behavior of UHMW polyethylene.

    PubMed

    Krzypow, D J; Rimnac, C M

    2000-10-01

    To increase the long-term performance of total joint replacements, finite element analyses of ultra high molecular weight polyethylene (UHMWPE) components have been conducted to predict the effect of load on the stress and strain distributions occurring on and within these components. Early models incorporated the monotonic behavior of UHMWPE without considering the unloading and cyclic loading behavior. However, UHMWPE components undergo cyclic loading during use and at least two wear damage modes (pitting and delamination) are thought to be associated with the fatigue fracture properties of UHMWPE. The objective of this study was to examine the fully reversed uniaxial tension/compression cyclic steady state stress-strain behavior of UHMWPE as a first step towards developing a cyclic constitutive relationship for UHMWPE. The hypothesis that cycling results in a permanent change in the stress-strain relationship, that is, that the cyclic steady state represents a new cyclically stabilized state, was examined. It was found that, like other ductile polymers, UHMWPE substantially cyclically softens under fully reversed uniaxial straining. More cyclic softening occurred in tension than in compression. Furthermore, cyclic steady state was attained, but not cyclic stability. It is suggested that it may be more appropriate to base a material constitutive relationship for UHMWPE for finite element analyses of components upon a cyclically modified stress-strain relationship. PMID:10966018

  10. Ideal MHD Stability of ITER Steady State Scenarios with ITBs

    SciTech Connect

    F.M. Poli, C.E. Kessel, S. Jardin, J. Manickam, M. Chance, J. Chen

    2011-07-27

    One of ITER goals is to demonstrate feasibility of continuous operations using non-inductive current drive. Two main candidates have been identified for advanced operations: the long duration, high neutron fluency hybrid scenario and the steady state scenario, both operating at a plasma current lower than the reference ELMy scenario [1][2] to minimize the required current drive. The steady state scenario targets plasmas with current 7-10 MA in the flat-top, 50% of which will be provided by the self-generated, pressure-driven bootstrap current. It has been estimated that, in order to obtain a fusion gain Q > 5 at a current of 9 MA, it should be ΒN > 2.5 and H > 1.5 [3]. This implies the presence of an Internal Transport Barrier (ITB). This work discusses how the stability of steady state scenarios with ITBs is affected by the external heating sources and by perturbations of the equilibrium profiles.

  11. Oxygen consumption dynamics in steady-state tumour models.

    PubMed

    Grimes, David Robert; Fletcher, Alexander G; Partridge, Mike

    2014-09-01

    Oxygen levels in cancerous tissue can have a significant effect on treatment response: hypoxic tissue is both more radioresistant and more chemoresistant than well-oxygenated tissue. While recent advances in medical imaging have facilitated real-time observation of macroscopic oxygenation, the underlying physics limits the resolution to the millimetre domain, whereas oxygen tension varies over a micrometre scale. If the distribution of oxygen in the tumour micro-environment can be accurately estimated, then the effect of potential dose escalation to these hypoxic regions could be better modelled, allowing more realistic simulation of biologically adaptive treatments. Reaction-diffusion models are commonly used for modelling oxygen dynamics, with a variety of functional forms assumed for the dependence of oxygen consumption rate (OCR) on cellular status and local oxygen availability. In this work, we examine reaction-diffusion models of oxygen consumption in spherically and cylindrically symmetric geometries. We consider two different descriptions of oxygen consumption: one in which the rate of consumption is constant and one in which it varies with oxygen tension in a hyperbolic manner. In each case, we derive analytic approximations to the steady-state oxygen distribution, which are shown to closely match the numerical solutions of the equations and accurately predict the extent to which oxygen can diffuse. The derived expressions relate the limit to which oxygen can diffuse into a tissue to the OCR of that tissue. We also demonstrate that differences between these functional forms are likely to be negligible within the range of literature estimates of the hyperbolic oxygen constant, suggesting that the constant consumption rate approximation suffices for modelling oxygen dynamics for most values of OCR. These approximations also allow the rapid identification of situations where hyperbolic consumption forms can result in significant differences from constant

  12. Startle response of captive North Sea fish species to underwater tones between 0.1 and 64 kHz.

    PubMed

    Kastelein, Ronald A; Heul, Sander van der; Verboom, Willem C; Jennings, Nancy; Veen, Jan van der; de Haan, Dick

    2008-06-01

    World-wide, underwater background noise levels are increasing due to anthropogenic activities. Little is known about the effects of anthropogenic noise on marine fish, and information is needed to predict any negative effects. Behavioural startle response thresholds were determined for eight marine fish species, held in a large tank, to tones of 0.1-64 kHz. Response threshold levels varied per frequency within and between species. For sea bass, the 50% reaction threshold occurred for signals of 0.1-0.7 kHz, for thicklip mullet 0.4-0.7 kHz, for pout 0.1-0.25 kHz, for horse mackerel 0.1-2 kHz and for Atlantic herring 4 kHz. For cod, pollack and eel, no 50% reaction thresholds were reached. Reaction threshold levels increased from approximately 100 dB (re 1 microPa, rms) at 0.1 kHz to approximately 160 dB at 0.7 kHz. The 50% reaction thresholds did not run parallel to the hearing curves. This shows that fish species react very differently to sound, and that generalisations about the effects of sound on fish should be made with care. As well as on the spectrum and level of anthropogenic sounds, the reactions of fish probably depend on the context (e.g. location, temperature, physiological state, age, body size, and school size). PMID:18295877

  13. Role of irregular otolith afferents in the steady-state nystagmus during off-vertical axis rotation

    NASA Technical Reports Server (NTRS)

    Angelaki, D. E.; Perachio, A. A.; Mustari, M. J.; Strunk, C. L.

    1992-01-01

    1. During constant velocity off-vertical axis rotations (OVAR) in the dark a compensatory ocular nystagmus is present throughout rotation despite the lack of a maintained signal from the semicircular canals. Lesion experiments and canal plugging have attributed the steady-state ocular nystagmus during OVAR to inputs from the otolith organs and have demonstrated that it depends on an intact velocity storage mechanism. 2. To test whether irregularly discharging otolith afferents play a crucial role in the generation of the steady-state eye nystagmus during OVAR, we have used anodal (inhibitory) currents bilaterally to selectively and reversibly block irregular vestibular afferent discharge. During delivery of DC anodal currents (100 microA) bilaterally to both ears, the slow phase eye velocity of the steady-state nystagmus during OVAR was reduced or completely abolished. The disruption of the steady-state nystagmus was transient and lasted only during the period of galvanic stimulation. 3. To distinguish a possible effect of ablation of the background discharge rates of irregular vestibular afferents on the velocity storage mechanism from specific contributions of the dynamic responses from irregular otolith afferents to the circuit responsible for the generation of the steady-state nystagmus, bilateral DC anodal galvanic stimulation was applied during optokinetic nystagmus (OKN) and optokinetic afternystagmus (OKAN). No change in OKN and OKAN was observed.(ABSTRACT TRUNCATED AT 250 WORDS).

  14. Increased Beta Frequency (15-30 Hz) Oscillatory Responses in Euthymic Bipolar Patients Under Lithium Monotherapy.

    PubMed

    Tan, Devran; Özerdem, Ayşegül; Güntekin, Bahar; Atagün, M Ilhan; Tülay, Elif; Karadağ, Figen; Başar, Erol

    2016-04-01

    The effect of lithium on neurocognition is not still fully explored. Brain oscillatory activity is altered in bipolar disorder. We aimed to assess the oscillatory responses of euthymic bipolar patients and how they are affected by lithium monotherapy. Event-related oscillations in response to visual target stimulus during an oddball paradigm in 16 euthymic drug-free and 13 euthymic lithium-treated bipolar patients were compared with 16 healthy controls. The maximum peak-to-peak amplitudes were measured for each subject's averaged beta (15-30 Hz) responses in the 0- to 300-ms time window over frontal (F3, Fz, F4), central (C3, Cz, C4), temporal (T7, T8), temporo-parietal (TP7, TP8), parietal (P3, Pz, P4), and occipital (O1, Oz, O2) areas. Patients under lithium monotherapy had significantly higher beta responses to visual target stimuli than healthy controls (P=.017) and drug-free patients (P=.015). The increase in beta response was observed at all electrode locations, however, the difference was statistically significant for the left (T7; P=.016) and right (T8; P=.031) temporal beta responses. Increased beta responses in drug-free patients and further significant increase in lithium-treated patients may be indicative of a core pathophysiological process of bipolar disorder and how it is affected by lithium. Whether the finding corresponds to lithium's corrective effect on the underlying pathology or to its neurocognitive side effect remains to be further explored. In either case, the finding is a sign that the oscillatory activity may be useful in tracking medication effect in bipolar disorder. PMID:25465436

  15. Analytical determination of transition time between transient and steady state water infiltration

    NASA Astrophysics Data System (ADS)

    Lassabatere, Laurent; Angulo-Jaramillo, Rafael; di Prima, Simone; Bagarello, Vincenzo; Iovino, Massimo

    2016-04-01

    The hydraulic characterization of soil hydraulic properties is a prerequisite to the modelling of flow in the vadose zone. Since many years, numerous methods were developed to determine soil hydraulic properties. Many of these methods rely on water infiltration experiments and their analysis using analytical or numerical models. At the beginning, most models were developed for water infiltration at steady state. These models had the advantage to be easy to develop from a theoretical point of view. Yet, many drawbacks remain including the need to wait for a long time, leading to time-consuming experiments, the risk to infiltrate water in large volumes of soil, leading to a response affected by soil variability, and the uncertainty regarding the attainment of steady state (i.e. constant infiltration rate). More recently, infiltration models and mathematical developments addressed the case of consecutive transient and steady states. Yet, one main problem remain. In the field, the operator is never sure about the state of water infiltration data. This paper present analytical formulations for the estimation of a transition time. We consider the model developed by Haverkamp et al. (1994) linking 1D infiltration flux to cumulative infiltration and related approximated expansions. An analytical method based on scaling is proposed to define transition time values in terms of both scaled cumulative infiltration and times. Dimensional times are then calculated for a large variety of soils and initial conditions. These time database can be considered as a relevant tool for the guidance for operators who conduct water infiltration experiments and wants to know when to stop and also for modelers who want to know how to select the data to fit transient or steady state models. Haverkamp, R., Ross, P. J., Smetten, K. R. J., Parlange, J. Y. (1994), Three-dimensional analysis of infiltration from the disc infiltrometer: 2 Physically based infiltration equation. Water Resour. Res

  16. A Series RCL Circuit Theory for Analyzing Non-Steady-State Water Uptake of Maize Plants

    PubMed Central

    Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi

    2014-01-01

    Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths. PMID:25335512

  17. A series RCL circuit theory for analyzing non-steady-state water uptake of maize plants.

    PubMed

    Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi

    2014-01-01

    Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths. PMID:25335512

  18. A Series RCL Circuit Theory for Analyzing Non-Steady-State Water Uptake of Maize Plants

    NASA Astrophysics Data System (ADS)

    Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi

    2014-10-01

    Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths.

  19. Steady-state and transient analysis of a squeeze film damper bearing for rotor stability

    NASA Technical Reports Server (NTRS)

    Barrett, L. E.; Gunter, E. J.

    1975-01-01

    A study of the steady-state and transient response of the squeeze film damper bearing is presented. Both the steady-state and transient equations for the hydrodynamic bearing forces are derived. The bearing equivalent stiffness and damping coefficients are determined by steady-state equations. These coefficients are used to find the bearing configuration which will provide the optimum support characteristics based on a stability analysis of the rotor-bearing system. The transient analysis of rotor-bearing systems is performed by coupling the bearing and journal equations and integrating forward in time. The effects of unbalance, cavitation, and retainer springs are included in the analysis. Methods of determining the stability of a rotor-bearing system under the influence of aerodynamic forces and internal shaft friction are discussed with emphasis on solving the system characteristic frequency equation and on producing stability maps. It is shown that for optimum stability and low force transmissability the squeeze bearing should operate at an eccentricity ratio epsilon 0.4.

  20. Steady-state analysis of a nonlinear rotor-housing system. [Space Shuttle Main Engine

    NASA Technical Reports Server (NTRS)

    Noah, S. T.; Kim, Y. B.

    1990-01-01

    The periodic steady state response of a high pressure oxygen turbopump (HBOTP) of a Space Shuttle main engine (SSME), involving a clearance between the bearing and housing carrier, is sought. A harmonic balance method utilizig Fast Fourier Transform (FFT) algorithm is developed for the analysis. An impedance method is used to reduce the number of degrees of freedom to the displacements at the bearing clearance. Harmonic and subharmonic responses to imbalance for various system parameters are studied. The results show that the computational technique developed in this study is an effective and flexible method for determining the stable and unstable periodic response of complex rotor-housing systems with clearance type nonlinearity.

  1. A Steady-State Mass Transfer Model of Removing CPAs from Cryopreserved Blood with Hollow Fiber Modules

    PubMed Central

    Ding, Weiping; Zhou, Xiaoming; Heimfeld, Shelly; Reems, Jo-Anna; Gao, Dayong

    2010-01-01

    Hollow fiber modules are commonly used to conveniently and efficiently remove cryoprotective agents (CPAs) from cryopreserved cell suspensions. In this paper, a steady-state model coupling mass transfers across cell and hollow fiber membranes is theoretically developed to evaluate the removal of CPAs from cryopreserved blood using hollow fiber modules. This steady-state model complements the unsteady-state model which was presented in our previous study. As the steady-state model, unlike the unsteady-state model, can be used to evaluate the effect of ultrafiltration flow rates on the clearance of CPAs. The steady-state model is validated by experimental results and then is compared with the unsteady-state model. Using the steady-state model, the effects of ultrafiltration flow rates, NaCl concentrations in dialysate, blood flow rates and dialysate flow rates on CPA concentration variation and cell volume response are investigated in detail. According to the simulative results, the osmotic damage of red blood cells (RBCs) can easily be reduced by increasing ultrafiltration flow rates, increasing NaCl concentrations in dialysate, increasing blood flow rates or decreasing dialysate flow rates. PMID:20524740

  2. Mimicking Nonequilibrium Steady States with Time-Periodic Driving

    NASA Astrophysics Data System (ADS)

    Raz, O.; Subaşı, Y.; Jarzynski, C.

    2016-04-01

    Under static conditions, a system satisfying detailed balance generically relaxes to an equilibrium state in which there are no currents. To generate persistent currents, either detailed balance must be broken or the system must be driven in a time-dependent manner. A stationary system that violates detailed balance evolves to a nonequilibrium steady state (NESS) characterized by fixed currents. Conversely, a system that satisfies instantaneous detailed balance but is driven by the time-periodic variation of external parameters—also known as a stochastic pump (SP)—reaches a periodic state with nonvanishing currents. In both cases, these currents are maintained at the cost of entropy production. Are these two paradigmatic scenarios effectively equivalent? For discrete-state systems, we establish a mapping between nonequilibrium stationary states and stochastic pumps. Given a NESS characterized by a particular set of stationary probabilities, currents, and entropy production rates, we show how to construct a SP with exactly the same (time-averaged) values. The mapping works in the opposite direction as well. These results establish a proof of principle: They show that stochastic pumps are able to mimic the behavior of nonequilibrium steady states, and vice versa, within the theoretical framework of discrete-state stochastic thermodynamics. Nonequilibrium steady states and stochastic pumps are often used to model, respectively, biomolecular motors driven by chemical reactions and artificial molecular machines steered by the variation of external, macroscopic parameters. Our results loosely suggest that anything a biomolecular machine can do, an artificial molecular machine can do equally well. We illustrate this principle by showing that kinetic proofreading, a NESS mechanism that explains the low error rates in biochemical reactions, can be effectively mimicked by a constrained periodic driving.

  3. Steady state free radical budgets and ozone photochemistry during TOPSE

    NASA Astrophysics Data System (ADS)

    Cantrell, Christopher A.; Mauldin, L.; Zondlo, M.; Eisele, F.; Kosciuch, E.; Shetter, R.; Lefer, B.; Hall, S.; Campos, T.; Ridley, B.; Walega, J.; Fried, A.; Wert, B.; Flocke, F.; Weinheimer, A.; Hannigan, J.; Coffey, M.; Atlas, E.; Stephens, S.; Heikes, B.; Snow, J.; Blake, D.; Blake, N.; Katzenstein, A.; Lopez, J.; Browell, E. V.; Dibb, J.; Scheuer, E.; Seid, G.; Talbot, R.

    2003-02-01

    A steady state model, constrained by a number of measured quantities, was used to derive peroxy radical levels for the conditions of the Tropospheric Ozone Production about the Spring Equinox (TOPSE) campaign. The analysis is made using data collected aboard the NCAR/NSF C-130 aircraft from February through May 2000 at latitudes from 40° to 85°N, and at altitudes from the surface to 7.6 km. HO2 + RO2 radical concentrations were measured during the experiment, which are compared with model results over the domain of the study showing good agreement on the average. Average measurement/model ratios are 1.04 (σ = 0.73) and 0.96 (σ = 0.52) for the MLB and HLB, respectively. Budgets of total peroxy radical levels as well as of individual free radical members were constructed, which reveal interesting differences compared to studies at lower latitudes. The midlatitude part of the study region is a significant net source of ozone, while the high latitudes constitute a small net sink leading to the hypothesis that transport from the middle latitudes can explain the observed increase in ozone in the high latitudes. Radical reservoir species concentrations are modeled and compared with the observations. For most conditions, the model does a good job of reproducing the formaldehyde observations, but the peroxide observations are significantly less than steady state for this study. Photostationary state (PSS) derived total peroxy radical levels and NO/NO2 ratios are compared with the measurements and the model; PSS-derived results are higher than observations or the steady state model at low NO concentrations.

  4. The requirements of a next step large steady state tokamak

    NASA Astrophysics Data System (ADS)

    Janeschitz, G.; Barabaschi, P.; Federici, G.; Ioki, K.; Ladd, P.; Mukhovatov, V.; Sugihara, M.; Tivey, R.; ITER-JCT; Home Team

    2000-06-01

    After a decision by the ITER parties to investigate the possibility of designing a reduced cost version of ITER several possible machine layouts with different aspect ratios were studied. Relatively early in this process it became clear that there is no significant cost difference between different aspect ratios and that there is a maximum realistically possible aspect ratio for a machine with 6 m major radius and rather high plasma shaping. Following this study a machine with an intermediate aspect ratio (3.1) called the ITER Fusion Energy Advanced Tokamak (ITER FEAT) was chosen as the basis for the outline design of a reduced cost ITER. Several potential steady state scenarios can be investigated in ITER FEAT, i.e. monotonic or reversed shear at full or reduced minor radius. In addition, so-called hybrid discharges, are feasible where a mixture of inductive and non-inductive current drive as well as bootstrap current allows long pulse discharges of the order of 2500 s. The βN values and H factors required for these discharges are in the same range as those observed on present machines, which provides confidence that such discharges can be studied in ITER FEAT. However, due to uncertainties in physics knowledge, for example the current drive efficiency off-axis, it is impossible at present to generate a completely self-consistent scenario taking all boundary conditions, for example engineering or heating system constraints, into account. In addition, all of these regimes have a potential problem with divertor operation compatibility (low edge density) and with helium exhaust which has to be addressed in existing experiments. For the engineering design of the in-vessel components and for the balance of the plant there is practically no difference between inductive (500 s) and steady state operation. However, the choice of heating systems and the distribution of power between them will be strongly influenced by the envisaged steady state scenarios.

  5. Skewness of steady-state current fluctuations in nonequilibrium systems

    NASA Astrophysics Data System (ADS)

    Belousov, Roman; Cohen, E. G. D.; Wong, Chun-Shang; Goree, John A.; Feng, Yan

    2016-04-01

    A skewness of the probability for instantaneous current fluctuations, in a nonequilibrium steady state, is observed experimentally in a dusty plasma. This skewness is attributed to the spatial asymmetry, which is imminent to the nonequilibrium systems due to the external hydrodynamic gradient. Using the modern framework of the large deviation theory, we extend the Onsager-Machlup ansatz for equilibrium fluctuations to systems with a preferred spatial direction, and provide a modulated Gaussian probability distribution, which is tested by simulations. This probability distribution is also of potential interest for other statistical disciplines. Connections with the principles of statistical mechanics, due to Boltzmann and Gibbs, are discussed as well.

  6. Ergodicity, mixing, and time reversibility for atomistic nonequilibrium steady states

    SciTech Connect

    Hoover, W.G.; Kum, O.

    1997-11-01

    Ergodic mixing is prerequisite to any statistical-mechanical calculation of properties derived from atomistic dynamical simulations. Thus the time-reversible thermostats and ergostats used in simulating Gibbsian equilibrium dynamics or nonequilibrium steady-state dynamics should impose ergodicity and mixing. Though it is hard to visualize many-dimensional phase-space distributions, recent developments provide several practical numerical approaches to the problem of ergodic mixing. Here we apply three of these approaches to a useful nonequilibrium test problem, an oscillator in a temperature gradient. {copyright} {ital 1997} {ital The American Physical Society}

  7. Tracking and controlling unstable steady states of dynamical systems

    NASA Astrophysics Data System (ADS)

    Tamaševičiūtė, Elena; Mykolaitis, Gytis; Bumelienė, Skaidra; Tamaševičius, Arūnas

    2014-03-01

    An adaptive controller for stabilization of unknown unstable steady states (spirals, nodes and saddles) of nonlinear dynamical systems is considered and its robustness under the changes of the location of the fixed point in the phase space is demonstrated. An analog electronic controller, based on a low-pass filter technique, is described. It can be easily switched between a stable and an unstable mode of operation for stabilizing either spirals/nodes or saddles, respectively. Numerical and experimental results for two autonomous systems, the damped Duffing-Holmes oscillator and the chaotic Lorenz system, are presented.

  8. Steady State Sedimentation in a Liquid Fluidized Bed

    NASA Technical Reports Server (NTRS)

    Segre, P. N.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The velocity fluctuations and the local particle concentration of a particle suspension exhibiting steady state sedimentation in a fluidized bed are determined as a function of height along the particle column. Both the velocity fluctuations and the particle volume fraction are found to strongly depend on height. We account for the stability of the bed by a simple model evoking a flux balance. Velocity fluctuations driving a downward particle flux are compensated by an upward particle flux stemming from an excess flow velocity due to the concentration gradient of the system.

  9. Steady-State Solution of a Flexible Wing

    NASA Technical Reports Server (NTRS)

    Karkehabadi, Reza; Chandra, Suresh; Krishnamurthy, Ramesh

    1997-01-01

    A fluid-structure interaction code, ENSAERO, has been used to compute the aerodynamic loads on a swept-tapered wing. The code has the capability of using Euler or Navier-Stokes equations. Both options have been used and compared in the present paper. In the calculation of the steady-state solution, we are interested in knowing how the flexibility of the wing influences the lift coefficients. If the results of a flexible wing are not affected by the flexibility of the wing significantly, one could consider the wing to be rigid and reduce the problem from fluid-structure interaction to a fluid problem.

  10. Quantum-classical correspondence in steady states of nonadiabatic systems

    SciTech Connect

    Fujii, Mikiya; Yamashita, Koichi

    2015-12-31

    We first present nonadiabatic path integral which is exact formulation of quantum dynamics in nonadiabatic systems. Then, by applying the stationary phase approximations to the nonadiabatic path integral, a semiclassical quantization condition, i.e., quantum-classical correspondence, for steady states of nonadiabatic systems is presented as a nonadiabatic trace formula. The present quantum-classical correspondence indicates that a set of primitive hopping periodic orbits, which are invariant under time evolution in the phase space of the slow degree of freedom, should be quantized. The semiclassical quantization is then applied to a simple nonadiabatic model and accurately reproduces exact quantum energy levels.

  11. Steady State Vacuum Ultraviolet Exposure Facility With Automated Calibration Capability

    NASA Technical Reports Server (NTRS)

    Stueber, Thomas J.; Sechkar, Edward A.; Dever, Joyce A.; Banks, Bruce A.

    2000-01-01

    NASA Glenn Research Center at Lewis Field designed and developed a steady state vacuum ultraviolet automated (SSVUVa) facility with in situ VUV intensity calibration capability. The automated feature enables a constant accelerated VUV radiation exposure over long periods of testing without breaking vacuum. This test facility is designed to simultaneously accommodate four isolated radiation exposure tests within the SSVUVa vacuum chamber. Computer-control of the facility for long, term continuous operation also provides control and recording of thermocouple temperatures, periodic recording of VUV lamp intensity, and monitoring of vacuum facility status. This paper discusses the design and capabilities of the SSVUVa facility.

  12. Long Pulse Operation on Tore-Supra: Towards Steady State

    SciTech Connect

    Moreau, P.; Bucalossi, J.; Brosset, C.; Dufour, E.; Loarer, T.; Monier-Garbet, P.; Pegourie, B.; Tsitrone, E.; Basiuk, V.; Bremond, S.; Chantant, M.; Colas, L.; Commaux, N.; Geraud, A.; Guirlet, R.; Gunn, J.; Hertout, P.; Hoang, G. T.; Kazarian, F.; Mazon, D.

    2006-01-15

    The experimental programme of Tore Supra is devoted to the study of technology and physics issues associated to long-duration high performance discharges. This new domain of operation requires simultaneously and in steady state: heat removal capability, particle exhaust, fully non-inductive current drive, advanced technology integration and real time plasma control. The long discharge allows for addressing new time scale physic such as the wall particle retention and erosion. Moreover, the physics of fully non-inductive discharges is full of novelty, namely: the MHD stability, the slow spontaneous oscillation of the central electron temperature or the outstanding inward particle pinch.

  13. Linear modeling of steady-state behavioral dynamics.

    PubMed Central

    Palya, William L; Walter, Donald; Kessel, Robert; Lucke, Robert

    2002-01-01

    The observed steady-state behavioral dynamics supported by unsignaled periods of reinforcement within repeating 2,000-s trials were modeled with a linear transfer function. These experiments employed improved schedule forms and analytical methods to improve the precision of the measured transfer function, compared to previous work. The refinements include both the use of multiple reinforcement periods that improve spectral coverage and averaging of independently determined transfer functions. A linear analysis was then used to predict behavior observed for three different test schedules. The fidelity of these predictions was determined. PMID:11831782

  14. A Spreadsheet Program for Steady-State Temperature Distributions

    SciTech Connect

    Hutchens, G.J.

    2000-11-01

    A desktop program is developed in Microsoft EXCEL using Visual Basic for Applications (VBA) to solve a two-dimensional steady state heat conduction problem with a radiation boundary condition. The resulting partial differential equation and boundary conditions are solved using finite difference techniques and the results are compared with a finite element solution using the commercially available software package MSC/THERMAL. The results from the two methods are found to be within 1 percent. The VBA solution demonstrates how spreadsheet programs, like EXCEL, can be used to solve practical engineering problems with good accuracy.

  15. Paleoenvironmental evolution in a steady state foredeep, Taiwan

    NASA Astrophysics Data System (ADS)

    Nagel, S.; Castelltort, S.; Willett, S. D.; Mouthereau, F.; Lin, A. T.; Granjeon, D.; Kaus, B.

    2012-04-01

    The evolution of mountain ranges to steady state is an important concept in the study of the interrelationships between climate, mountain building and topography. The young and active Taiwan orogeny situated in the western pacific typhoon belt has often been regarded as the type locality of a steady state orogeny, and an ideal case study for tectonic and climatic geomorphology. One prediction of the steady-state theory applied to mountains is the attainment of a constant sediment flux. Our aim in the present study is to estimate the material flux out of the Taiwan orogeny through its evolution. To do so, we have studied the basin wide sedimentary facies distribution at five key stratigraphic horizons to construct detailed paleogeographic maps that include paleobathymetric information and sediment feeding systems. The maps highlight the complicated basin-wide dynamics of sediment dispersal within an evolving foreland basin. The basin physiography changed very little from the middle Miocene (around 12.5 Ma) to the late Pliocene (around 3 Ma); the paleoenvironments were essentially maintained from the passive margin to the foreland basin stage. At 3 Ma, during deposition of the mud-dominated Chinshui Shale, the main depositional basin started to widen and deepen. This clearly marks the increased subsidence associated with the approach of the growing orogen to the east. The basin started to become filled in the late early Pleistocene when a shallow marine wedge in front of the growing orogen initiated to propagate towards the south. We use Dionisos, a forward stratigraphic model, to simulate the evolution of the Taiwan foreland basin in terms of sediment flux (in and out of the basin) towards steady state. We constrain the model with our paleogeographic and sedimentary reconstructions. As an initial input data we utilize the paleoenvironmental maps and a primary sediment supply from the hinterland (topography). The model enables us to look at the long-term basin

  16. Steady state simulator using alternate left right approach

    NASA Astrophysics Data System (ADS)

    Ng, Yit Hoe; Hasan, Mohammad Khatim

    2013-04-01

    Partial difference equation plays important role in simulating a wide variety of science and engineering problem. In this paper, we develop numerical application which implements the iterative methods for steady state simulation and its numerical engine. A new approach names Alternate Left Right is applied onto Successive Overrelaxation (SOR) called as the Alternate Left Right Successive Overrelaxation (ALRSOR) iterative method. The experiment's results are compared amongst SOR and ALRSOR to reveal the performance of these numerical engines. From the results, Alternate Left Right approach successfully increases the speed computation. In conclusion, ALRSOR method performs the fastest amongst the compared method.

  17. Steady-State Motion Visual Evoked Potentials Produced by Oscillating Newton's Rings: Implications for Brain-Computer Interfaces

    PubMed Central

    Xie, Jun; Xu, Guanghua; Wang, Jing; Zhang, Feng; Zhang, Yizhuo

    2012-01-01

    In this study, we utilize a special visual stimulation protocol, called motion reversal, to present a novel steady-state motion visual evoked potential (SSMVEP)-based BCI paradigm that relied on human perception of motions oscillated in two opposite directions. Four Newton's rings with the oscillating expansion and contraction motions served as visual stimulators to elicit subjects' SSMVEPs. And four motion reversal frequencies of 8.1, 9.8, 12.25 and 14 Hz were tested. According to Canonical Correlation Analysis (CCA), the offline accuracy and ITR (mean ± standard deviation) over six healthy subjects were 86.56±9.63% and 15.93±3.83 bits/min, respectively. All subjects except one exceeded the level of 80% mean accuracy. Circular Hotelling's T-Squared test () also demonstrated that most subjects exhibited significantly strong stimulus-locked SSMVEP responses. The results of declining exponential fittings exhibited low-adaptation characteristics over the 100-s stimulation sequences in most experimental conditions. Taken together, these results suggest that the proposed paradigm can provide comparable performance with low-adaptation characteristic and less visual discomfort for BCI applications. PMID:22724028

  18. Nonequilibrium many-body steady states via Keldysh formalism

    NASA Astrophysics Data System (ADS)

    Maghrebi, Mohammad F.; Gorshkov, Alexey V.

    2016-01-01

    Many-body systems with both coherent dynamics and dissipation constitute a rich class of models which are nevertheless much less explored than their dissipationless counterparts. The advent of numerous experimental platforms that simulate such dynamics poses an immediate challenge to systematically understand and classify these models. In particular, nontrivial many-body states emerge as steady states under nonequilibrium dynamics. While these states and their phase transitions have been studied extensively with mean-field theory, the validity of the mean-field approximation has not been systematically investigated. In this paper, we employ a field-theoretic approach based on the Keldysh formalism to study nonequilibrium phases and phase transitions in a variety of models. In all cases, a complete description via the Keldysh formalism indicates a partial or complete failure of the mean-field analysis. Furthermore, we find that an effective temperature emerges as a result of dissipation, and the universal behavior including the dynamics near the steady state is generically described by a thermodynamic universality class.

  19. Non-steady state tidal heating of Enceladus

    NASA Astrophysics Data System (ADS)

    Shoji, D.; Hussmann, H.; Sohl, F.; Kurita, K.

    2014-06-01

    Enceladus is one of the most geologically active bodies in the Solar System. The satellite's diverse surface suggests that Enceladus was subject to past episodic heating. It is largely probable that the activity of Enceladus is not in a steady state. In order to analyze the non-steady state heating, thermal and orbital coupled calculation is needed because they affect each other. We perform the coupled calculation assuming conductive ice layer and low melting temperature. Although the heating state of Enceladus strongly depends on the rheological parameters used, episodic heating is induced if the Q-value of Saturn is less than 23,000 and Enceladus' core radius is less than 161 km. The duration of one episodic heating cycle is around one hundred million years. The cyclic change in ice thickness is consistent with the origin of a partial ocean which is suggested by plume emissions and diverse surface states of Enceladus. Although the obtained tidal heating rate is smaller than the observed heat flux of a few giga watt, other heating mechanisms involving e.g., liquid water and/or specific chemical reactions may be initiated by the formation of a partial or global subsurface ocean.

  20. Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism

    PubMed Central

    Fleming, R.M.T.; Thiele, I.; Provan, G.; Nasheuer, H.P.

    2010-01-01

    The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in E. coli and compare favourably with in silico prediction by flux balance analysis. PMID:20230840

  1. Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.

    PubMed

    Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P

    2010-06-01

    The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in Escherichia coli and compare favourably with in silico prediction by flux balance analysis. PMID:20230840

  2. Steady-state wear and friction in boundary lubrication studies

    NASA Technical Reports Server (NTRS)

    Loomis, W. R.; Jones, W. R., Jr.

    1980-01-01

    A friction and wear study was made at 20 C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25 min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible steady-state wear rates and steady-state friction coefficients were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods.

  3. Drug Sanctuaries, Low Steady State Viral Loads and Viral Blips.

    SciTech Connect

    Perelson, Alan S.,; Callaway, D.; Pomerantz, R. J.; Chen, H. Y.; Markowitz, M.; Ho, David D.; Di Mascio, M.

    2002-01-01

    Patients on HAART for long periods of time obtain viral loads (VLs) below 50 copies/ml. Ultrasensitive VL assays show that some of these patients obtain a low steady state VL, while others continue to exhibit VL declines to below 5 copies/ml. Low steady states can be explained by two-compartment models that incorporate a drug sanctuary. Interestingly, when patients exhibit continued declines below 50 copies/ml the rate of decline has a half-life of {approx} 6 months, consistent with some estimates of the rate of latent cell decline. Some patients, despite having sustained undetectable VLs show periods of transient viremia (blips). I will present some statistical characterization of the blips observed in a set of 123 patients, suggesting that blips are generated largely by random processes, that blips tend to correspond to periods of a few weeks in which VLs are elevated, and that VL decay from the peak of a blip may have two-phases. Using new results suggesting that the viral burst size, N {approx} 5 x 10{sup 4}, we estimate the number of cells needed to produce a blip.

  4. Zeroth law and nonequilibrium thermodynamics for steady states in contact

    NASA Astrophysics Data System (ADS)

    Chatterjee, Sayani; Pradhan, Punyabrata; Mohanty, P. K.

    2015-06-01

    We ask what happens when two nonequilibrium systems in steady state are kept in contact and allowed to exchange a quantity, say mass, which is conserved in the combined system. Will the systems eventually evolve to a new stationary state where a certain intensive thermodynamic variable, like equilibrium chemical potential, equalizes following the zeroth law of thermodynamics and, if so, under what conditions is it possible? We argue that an equilibriumlike thermodynamic structure can be extended to nonequilibrium steady states having short-ranged spatial correlations, provided that the systems interact weakly to exchange mass with rates satisfying a balance condition—reminiscent of a detailed balance condition in equilibrium. The short-ranged correlations would lead to subsystem factorization on a coarse-grained level and the balance condition ensures both equalization of an intensive thermodynamic variable as well as ensemble equivalence, which are crucial for construction of a well-defined nonequilibrium thermodynamics. This proposition is proved and demonstrated in various conserved-mass transport processes having nonzero spatial correlations.

  5. Driven, steady-state RFP computations. [reversed field pinch

    NASA Technical Reports Server (NTRS)

    Dahlburg, J. P.; Montgomery, D.; Doolen, G. D.; Turner, L.

    1988-01-01

    The pseudospectral three-dimensional MHD code of Dahlburg et al. (1986 and 1987) is used to compute the dynamical behavior of a channel of magnetofluid carrying an axial current and magnetic flux. This situation contains the essential MHD behavior of the reversed-field pinch (RFP). An externally imposed electric field is applied to an initially current-free magnetofluid and drives currents that rise and eventually fluctuate about values corresponding to pinch ratios Theta of about 1.3, 2.2, and 4.5. A period of violent turbulence leads to an approximately force-free core, surrounded by an active MHD boundary layer that is not force-free. A steady state is reached that can apparently be sustained indefinitely (for several hundred Alfven transit times or longer). The turbulence level and time variability in the steady state increase with increasing Theta. The average toroidal magnetic field at the wall reverses for Theta = 2.2 and 4.5, but not for Theta = 1.3. Negative toroidal current filaments are observed. The Lundquist numbers are of the order of a few hundred.

  6. Steady state magnetic field configurations for the earth's magnetotail

    SciTech Connect

    Hau, L.N.; Wolf, R.A.; Voigt, G.H. ); Wu, C.C. )

    1989-02-01

    The authors present a two-dimensional, force-balanced magnetic field model in which flux tubes have constant pV{gamma} throughout an extended region of the nightside plasma sheet, between approximately 36 R{sub E} geocentric distance and the region of the inner edge of the plasma sheet. They have thus demonstrated the theoretical existence of a steady state magnetic field configuration that is force-balanced and also consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD (isotropic pressure, perfect conductivity). The numerical solution was constructed for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The primary characteristics of the steady state convection solution are (1) a pressure maximum just tailward of the inner edge of the plasma sheet and (2) a deep, broad minimum in equatorial magnetic field strength B{sub ze}, also just tailward of the inner edge. The results are consistent with Erickson's (1985) convection time sequences, which exhibited analogous pressure peaks and B{sub ze} minima. Observations do not indicate the existence of a B{sub ze} minimum, on the average. They suggest that the configurations with such deep minima in B{sub ze} may be tearing-mode unstable, thus leading to substorm onset in the inner plasma sheet.

  7. Steady-State ALPS for Real-Valued Problems

    NASA Technical Reports Server (NTRS)

    Hornby, Gregory S.

    2009-01-01

    The two objectives of this paper are to describe a steady-state version of the Age-Layered Population Structure (ALPS) Evolutionary Algorithm (EA) and to compare it against other GAs on real-valued problems. Motivation for this work comes from our previous success in demonstrating that a generational version of ALPS greatly improves search performance on a Genetic Programming problem. In making steady-state ALPS some modifications were made to the method for calculating age and the method for moving individuals up layers. To demonstrate that ALPS works well on real-valued problems we compare it against CMA-ES and Differential Evolution (DE) on five challenging, real-valued functions and on one real-world problem. While CMA-ES and DE outperform ALPS on the two unimodal test functions, ALPS is much better on the three multimodal test problems and on the real-world problem. Further examination shows that, unlike the other GAs, ALPS maintains a genotypically diverse population throughout the entire search process. These findings strongly suggest that the ALPS paradigm is better able to avoid premature convergence then the other GAs.

  8. Gas-turbine engine steady-state behavior

    NASA Astrophysics Data System (ADS)

    Curnock, Barry

    A set of graphics with explanations illustrating gas turbine engine steady state behavior are presented. Typical combinations of compressors and nozzles which occur in a gas turbine engine are shown. The basic effect of a nozzle is explained by considering a compressor on a test rig: typical compressor, fan, and turbine characteristics are illustrated. The following are discussed: the degrees of freedom of an aeroengine (the flow and the power); the 'working lines' of components (the locus of the off design steady state operating points of a component plotted on a chart of that components characteristics); bleed and whirl; offtakes; P1 effects (performance changes which modify the basic nondimensional behavior an engine (caused by the effect on Reynolds number levels and on engine mechanical configuration of basic engine inlet pressure level)), and T1 effects (performance changes which modify the basic nondimensional behavior of an engine and are caused by the effects of engine inlet temperature level on Reynolds number level, on engine mechanical configuration and on specific heat level); variable nozzles; and turbojet matching.

  9. Steady State Erosion of Granular Particles by Shear Flow

    NASA Astrophysics Data System (ADS)

    Allen, Benjamin; Kudrolli, Arshad

    2015-11-01

    Despite decades of scientific observation of rivers, streams and laboratory experiments the process of erosion still is not understood. Empirical fits are used to determine when erosion starts with more than an order of magnitude scatter or a shifting power law determining how much material erodes away. In order to study the many body problem of multiple particles we first need to understand the basics of a single particle eroding from a potential well in laminar flow. Using different particle densities and different barrier heights we looked at the onset of erosion and the balance of forces and torques to create a predictive model of when a single particle will erode over a barrier of a given height as a function of shear rate and viscosity. We then create a steady state system in which to image erosion as it happens and simultaneously measure flow velocity and particle movement. Measuring particle movement allows us to determine when steady state erosion occurs and calculate the fluxes and slip velocities at the beginning of the erosion process as we transition from rolling particles to particles suspended in the fluid flow. NSF Grant Number CBET 1335928.

  10. Characterization of the Prostate-Specific Antigen (PSA) Catalytic Mechanism: A Pre-Steady-State and Steady-State Study

    PubMed Central

    Tomao, Luigi; Sbardella, Diego; Gioia, Magda; Di Masi, Alessandra; Marini, Stefano; Ascenzi, Paolo; Coletta, Massimo

    2014-01-01

    Prostate-specific antigen (PSA), an enzyme of 30 kDa grouped in the kallikrein family is synthesized to high levels by normal and malignant prostate epithelial cells. Therefore, it is the main biomarker currently used for early diagnosis of prostate cancer. Here, presteady-state and steady-state kinetics of the PSA-catalyzed hydrolysis of the fluorogenic substrate Mu-His-Ser-Ser-Lys-Leu-Gln-AMC (spanning from pH 6.5 to pH 9.0, at 37.0°C) are reported. Steady-state kinetics display at every pH value a peculiar feature, represented by an initial “burst” phase of the fluorescence signal before steady-state conditions are taking place. This behavior, which has been already observed in other members of the kallikrein family, suggests the occurrence of a proteolytic mechanism wherefore the acylation step is faster than the deacylation process. This feature allows to detect the acyl intermediate, where the newly formed C-terminal carboxylic acid of the cleaved substrate forms an ester bond with the -OH group of the Ser195 catalytic residue, whereas the AMC product has been already released. Therefore, the pH-dependence of the two enzymatic steps (i.e., acylation and deacylation) has been separately characterized, allowing the determination of pKa values. On this basis, possible residues are tentatively identified in PSA, which might regulate these two steps by interacting with the two portions of the substrate. PMID:25068395