Electromagnetic pulse propagation in dispersive planar dielectrics.

PubMed

Moten, K; Durney, C H; Stockham, T G

1989-01-01

The responses of a plane-wave pulse train irradiating a lossy dispersive dielectric half-space are investigated. The incident pulse train is expressed as a Fourier series with summing done by the inverse fast Fourier transform. The Fourier series technique is adopted to avoid the many difficulties often encountered in finding the inverse Fourier transform when transform analyses are used. Calculations are made for propagation in pure water, and typical waveforms inside the dielectric half-space are presented. Higher harmonics are strongly attenuated, resulting in a single continuous sinusoidal waveform at the frequency of the fundamental depth in the material. The time-averaged specific absorption rate (SAR) for pulse-train propagation is shown to be the sum of the time-averaged SARs of the individual harmonic components of the pulse train. For the same average power, calculated SARs reveal that pulse trains generally penetrate deeper than carrier-frequency continuous waves but not deeper than continuous waves at frequencies approaching the fundamental of the pulse train. The effects of rise time on the propagating pulse train in the dielectrics are shown and explained. Since most practical pulsed systems are very limited in bandwidth, no pronounced differences between their response and continuous wave (CW) response would be expected. Typical results for pulse-train propagation in arrays of dispersive planar dielectric slabs are presented. Expressing the pulse train as a Fourier series provides a practical way of interpreting the dispersion characteristics from the spectral point of view.

Chaotic carrier pulse position modulation communication system and method

DOEpatents

Abarbanel, Henry D. I.; Larson, Lawrence E.; Rulkov, Nikolai F.; Sushchik, Mikhail M.; Tsimring, Lev S.; Volkovskii, Alexander R.

2001-01-01

A chaotic carrier pulse position modulation communication system and method is disclosed. The system includes a transmitter and receiver having matched chaotic pulse regenerators. The chaotic pulse regenerator in the receiver produces a synchronized replica of a chaotic pulse train generated by the regenerator in the transmitter. The pulse train from the transmitter can therefore act as a carrier signal. Data is encoded by the transmitter through selectively altering the interpulse timing between pulses in the chaotic pulse train. The altered pulse train is transmitted as a pulse signal. The receiver can detect whether a particular interpulse interval in the pulse signal has been altered by reference to the synchronized replica it generates, and can therefore detect the data transmitted by the receiver. Preferably, the receiver predicts the earliest moment in time it can expect a next pulse after observation of at least two consecutive pulses. It then decodes the pulse signal beginning at a short time before expected arrival of a pulse.

Laser-induced periodic surface structures on 6H-SiC single crystals using temporally delayed femtosecond laser double-pulse trains

NASA Astrophysics Data System (ADS)

Song, Juan; Tao, Wenjun; Song, Hui; Gong, Min; Ma, Guohong; Dai, Ye; Zhao, Quanzhong; Qiu, Jianrong

2016-04-01

In this paper, a time-delay-adjustable double-pulse train with 800-nm wavelength, 200-fs pulse duration and a repetition rate of 1 kHz, produced by a collinear two-beam optical system like a Mach-Zehnder interferometer, was employed for irradiation of 6H-SiC crystal. The dependence of the induced structures on time delay of double-pulse train for parallel-polarization configuration was studied. The results show that as the time delay of collinear parallel-polarization dual-pulse train increased, the induced near-subwavelength ripples (NSWRs) turn from irregular rippled pattern to regularly periodic pattern and have their grooves much deepened. The characteristics timescale for this transition is about 6.24 ps. Besides, the areas of NSWR were found to decay exponentially for time delay from 0 to 1.24 ps and then slowly increase for time delay from 1.24 to 14.24 ps. Analysis shows that multiphoton ionization effect, grating-assisted surface plasmon coupling effect, and timely intervene of second pulse in a certain physical stage experienced by 6H-SiC excited upon first pulse irradiation may contribute to the transition of morphology details.

The relation between auditory-nerve temporal responses and perceptual rate integration in cochlear implants

PubMed Central

Hughes, Michelle L.; Baudhuin, Jacquelyn L.; Goehring, Jenny L.

2014-01-01

The purpose of this study was to examine auditory-nerve temporal response properties and their relation to psychophysical threshold for electrical pulse trains of varying rates (“rate integration”). The primary hypothesis was that better rate integration (steeper slope) would be correlated with smaller decrements in ECAP amplitude as a function of stimulation rate (shallower slope of the amplitude-rate function), reflecting a larger percentage of the neural population contributing more synchronously to each pulse in the train. Data were obtained for 26 ears in 23 cochlear-implant recipients. Electrically evoked compound action potential (ECAP) amplitudes were measured in response to each of 21 pulses in a pulse train for the following rates: 900, 1200, 1800, 2400, and 3500 pps. Psychophysical thresholds were obtained using a 3-interval, forced-choice adaptive procedure for 300-ms pulse trains of the same rates as used for the ECAP measures, which formed the rate-integration function. For each electrode, the slope of the psychophysical rate-integration function was compared to the following ECAP measures: (1) slope of the function comparing average normalized ECAP amplitude across pulses versus stimulation rate (“adaptation”), (2) the rate that produced the maximum alternation depth across the pulse train, and (3) rate at which the alternating pattern ceased (stochastic rate). Results showed no significant relations between the slope of the rate-integration function and any of the ECAP measures when data were collapsed across subjects. However, group data showed that both threshold and average ECAP amplitude decreased with increased stimulus rate, and within-subject analyses showed significant positive correlations between psychophysical thresholds and mean ECAP response amplitudes across the pulse train. These data suggest that ECAP temporal response patterns are complex and further study is required to better understand the relative contributions of adaptation, desynchronization, and firing probabilities of individual neurons that contribute to the aggregate ECAP response. PMID:25093283

Measurement and Control of Attosecond Pulses

DTIC Science & Technology

2016-04-25

high harmonic train in the medium but each pulse in the train is travelling in a different direction. Therefore, as the beam propagates, it...pulses in the far field. The train of pulses created in this way are shown in the plot of angle of the radiation (vertical axis) as a function of

Systems and methods for selective detection and imaging in coherent Raman microscopy by spectral excitation shaping

DOEpatents

Xie, Xiaoliang Sunney; Freudiger, Christian; Min, Wei

2016-03-15

A microscopy imaging system is disclosed that includes a light source system, a spectral shaper, a modulator system, an optics system, an optical detector and a processor. The light source system is for providing a first train of pulses and a second train of pulses. The spectral shaper is for spectrally modifying an optical property of at least some frequency components of the broadband range of frequency components such that the broadband range of frequency components is shaped producing a shaped first train of pulses to specifically probe a spectral feature of interest from a sample, and to reduce information from features that are not of interest from the sample. The modulator system is for modulating a property of at least one of the shaped first train of pulses and the second train of pulses at a modulation frequency. The optical detector is for detecting an integrated intensity of substantially all optical frequency components of a train of pulses of interest transmitted or reflected through the common focal volume. The processor is for detecting a modulation at the modulation frequency of the integrated intensity of substantially all of the optical frequency components of the train of pulses of interest due to the non-linear interaction of the shaped first train of pulses with the second train of pulses as modulated in the common focal volume, and for providing an output signal for a pixel of an image for the microscopy imaging system.

Effect of inter-train interval on the induction of repetition suppression of motor-evoked potentials using transcranial magnetic stimulation.

PubMed

Pitkänen, Minna; Kallioniemi, Elisa; Julkunen, Petro

2017-01-01

Repetition suppression (RS) is evident as a weakened response to repeated stimuli after the initial response. RS has been demonstrated in motor-evoked potentials (MEPs) induced with transcranial magnetic stimulation (TMS). Here, we investigated the effect of inter-train interval (ITI) on the induction of RS of MEPs with the attempt to optimize the investigative protocols. Trains of TMS pulses, targeted to the primary motor cortex by neuronavigation, were applied at a stimulation intensity of 120% of the resting motor threshold. The stimulus trains included either four or twenty pulses with an inter-stimulus interval (ISI) of 1 s. The ITI was here defined as the interval between the last pulse in a train and the first pulse in the next train; the ITIs used here were 1, 3, 4, 6, 7, 12, and 17 s. RS was observed with all ITIs except with the ITI of 1 s, in which the ITI was equal to ISI. RS was more pronounced with longer ITIs. Shorter ITIs may not allow sufficient time for a return to baseline. RS may reflect a startle-like response to the first pulse of a train followed by habituation. Longer ITIs may allow more recovery time and in turn demonstrate greater RS. Our results indicate that RS can be studied with confidence at relatively short ITIs of 6 s and above.

Effects of acoustic noise on the auditory nerve compound action potentials evoked by electric pulse trains.

PubMed

Nourski, Kirill V; Abbas, Paul J; Miller, Charles A; Robinson, Barbara K; Jeng, Fuh-Cherng

2005-04-01

This study investigated the effects of acoustic noise on the auditory nerve compound action potentials in response to electric pulse trains. Subjects were adult guinea pigs, implanted with a minimally invasive electrode to preserve acoustic sensitivity. Electrically evoked compound action potentials (ECAP) were recorded from the auditory nerve trunk in response to electric pulse trains both during and after the presentation of acoustic white noise. Simultaneously presented acoustic noise produced a decrease in ECAP amplitude. The effect of the acoustic masker on the electric probe was greatest at the onset of the acoustic stimulus and it was followed by a partial recovery of the ECAP amplitude. Following cessation of the acoustic noise, ECAP amplitude recovered over a period of approximately 100-200 ms. The effects of the acoustic noise were more prominent at lower electric pulse rates (interpulse intervals of 3 ms and higher). At higher pulse rates, the ECAP adaptation to the electric pulse train alone was larger and the acoustic noise, when presented, produced little additional effect. The observed effects of noise on ECAP were the greatest at high electric stimulus levels and, for a particular electric stimulus level, at high acoustic noise levels.

Microscopy imaging system and method employing stimulated raman spectroscopy as a contrast mechanism

DOEpatents

Xie, Xiaoliang Sunney [Lexington, MA; Freudiger, Christian [Boston, MA; Min, Wei [Cambridge, MA

2011-09-27

A microscopy imaging system includes a first light source for providing a first train of pulses at a first center optical frequency .omega..sub.1, a second light source for providing a second train of pulses at a second center optical frequency .omega..sub.2, a modulator system, an optical detector, and a processor. The modulator system is for modulating a beam property of the second train of pulses at a modulation frequency f of at least 100 kHz. The optical detector is for detecting an integrated intensity of substantially all optical frequency components of the first train of pulses from the common focal volume by blocking the second train of pulses being modulated. The processor is for detecting, a modulation at the modulation frequency f, of the integrated intensity of the optical frequency components of the first train of pulses to provide a pixel of an image for the microscopy imaging system.

Lifebox pulse oximeter implementation in Malawi: evaluation of educational outcomes and impact on oxygen desaturation episodes during anaesthesia.

PubMed

Albert, V; Mndolo, S; Harrison, E M; O'Sullivan, E; Wilson, I H; Walker, I A

2017-06-01

Pulse oximetry is an essential monitor for safe anaesthesia but is often not available in low-income countries. The aim of this study was to determine whether the introduction of pulse oximetry with training was feasible and could reduce the incidence of oxygen desaturation during anaesthesia in a low-income country. Pulse oximeters were donated, with training, to 83 non-physician anaesthetists in Malawi. Knowledge was tested immediately before and after training and at follow-up. Providers were asked to record the lowest peripheral oxygen saturation (SpO 2 ) for the first 100 cases anaesthetised after training. The primary clinical outcome was the proportion of cases with an oxygen desaturation event (SpO 2 < 90%). Seventy-seven of 83 (93%) participants completed all pre- and post-training tests. Pulse oximetry knowledge improved after training from a median (IQR [range]) score of 39 (37-42 [28-48]) to 44 (42-46 [35-50]) and this knowledge was maintained for 8 months (p < 0.001). Oxygen saturation data and provider responses were recorded for 4772 cases. The proportion of oxygen desaturation episodes decreased from 17.2% to 6.5%, representing a 36% reduction in the odds of an oxygen desaturation event in the second 50 cases compared with the first 50 (OR 0.64, 95%CI 0.50-0.82, p < 0.001). We conclude that donation of pulse oximeters, with training, in Malawi was feasible, improved knowledge and reduced the incidence of oxygen desaturation events. © 2017 The Association of Anaesthetists of Great Britain and Ireland.

Effect of Pulse Rate on Loudness Discrimination in Cochlear Implant Users.

PubMed

Azadpour, Mahan; McKay, Colette M; Svirsky, Mario A

2018-03-12

Stimulation pulse rate affects current amplitude discrimination by cochlear implant (CI) users, indicated by the evidence that the JND (just noticeable difference) in current amplitude delivered by a CI electrode becomes larger at higher pulse rates. However, it is not clearly understood whether pulse rate would affect discrimination of speech intensities presented acoustically to CI processors, or what the size of this effect might be. Intensity discrimination depends on two factors: the growth of loudness with increasing sound intensity and the loudness JND (or the just noticeable loudness increment). This study evaluated the hypothesis that stimulation pulse rate affects loudness JND. This was done by measuring current amplitude JNDs in an experiment design based on signal detection theory according to which loudness discrimination is related to internal noise (which is manifested by variability in loudness percept in response to repetitions of the same physical stimulus). Current amplitude JNDs were measured for equally loud pulse trains of 500 and 3000 pps (pulses per second) by increasing the current amplitude of the target pulse train until it was perceived just louder than a same-rate or different-rate reference pulse train. The JND measures were obtained at two presentation levels. At the louder level, the current amplitude JNDs were affected by the rate of the reference pulse train in a way that was consistent with greater noise or variability in loudness perception for the higher pulse rate. The results suggest that increasing pulse rate from 500 to 3000 pps can increase loudness JND by 60 % at the upper portion of the dynamic range. This is equivalent to a 38 % reduction in the number of discriminable steps for acoustic and speech intensities.

Techniques for decoding speech phonemes and sounds: A concept

NASA Technical Reports Server (NTRS)

Lokerson, D. C.; Holby, H. G.

1975-01-01

Techniques studied involve conversion of speech sounds into machine-compatible pulse trains. (1) Voltage-level quantizer produces number of output pulses proportional to amplitude characteristics of vowel-type phoneme waveforms. (2) Pulses produced by quantizer of first speech formants are compared with pulses produced by second formants.

Temporal selectivity by single neurons in the torus semicircularis of Batrachyla antartandica (Amphibia: Leptodactylidae).

PubMed

Penna, M; Lin, W Y; Feng, A S

2001-12-01

We investigated the response selectivities of single auditory neurons in the torus semicircularis of Batrachyla antartandica (a leptodactylid from southern Chile) to synthetic stimuli having diverse temporal structures. The advertisement call for this species is characterized by a long sequence of brief sound pulses having a dominant frequency of about 2000 Hz. We constructed five different series of synthetic stimuli in which the following acoustic parameters were systematically modified, one at a time: pulse rate, pulse duration, pulse rise time, pulse fall time, and train duration. The carrier frequency of these stimuli was fixed at the characteristic frequency of the units under study (n=44). Response patterns of TS units to these synthetic call variants revealed different degrees of selectivity for each of the temporal variables. A substantial number of neurons showed preference for pulse rates below 2 pulses s(-1), approximating the values found in natural advertisement calls. Tonic neurons generally showed preferences for long pulse durations, long rise and fall times, and long train durations. In contrast, phasic and phasic-burst neurons preferred stimuli with short duration, short rise and fall times and short train durations.

Vibrotactile sensory substitution for object manipulation: amplitude versus pulse train frequency modulation.

PubMed

Stepp, Cara E; Matsuoka, Yoky

2012-01-01

Incorporating sensory feedback with prosthetic devices is now possible, but the optimal methods of providing such feedback are still unknown. The relative utility of amplitude and pulse train frequency modulated stimulation paradigms for providing vibrotactile feedback for object manipulation was assessed in 10 participants. The two approaches were studied during virtual object manipulation using a robotic interface as a function of presentation order and a simultaneous cognitive load. Despite the potential pragmatic benefits associated with pulse train frequency modulated vibrotactile stimulation, comparison of the approach with amplitude modulation indicates that amplitude modulation vibrotactile stimulation provides superior feedback for object manipulation.

Virtual active touch using randomly patterned intracortical microstimulation.

PubMed

O'Doherty, Joseph E; Lebedev, Mikhail A; Li, Zheng; Nicolelis, Miguel A L

2012-01-01

Intracortical microstimulation (ICMS) has promise as a means for delivering somatosensory feedback in neuroprosthetic systems. Various tactile sensations could be encoded by temporal, spatial, or spatiotemporal patterns of ICMS. However, the applicability of temporal patterns of ICMS to artificial tactile sensation during active exploration is unknown, as is the minimum discriminable difference between temporally modulated ICMS patterns. We trained rhesus monkeys in an active exploration task in which they discriminated periodic pulse-trains of ICMS (200 Hz bursts at a 10 Hz secondary frequency) from pulse trains with the same average pulse rate, but distorted periodicity (200 Hz bursts at a variable instantaneous secondary frequency). The statistics of the aperiodic pulse trains were drawn from a gamma distribution with mean inter-burst intervals equal to those of the periodic pulse trains. The monkeys distinguished periodic pulse trains from aperiodic pulse trains with coefficients of variation 0.25 or greater. Reconstruction of movement kinematics, extracted from the activity of neuronal populations recorded in the sensorimotor cortex concurrent with the delivery of ICMS feedback, improved when the recording intervals affected by ICMS artifacts were removed from analysis. These results add to the growing evidence that temporally patterned ICMS can be used to simulate a tactile sense for neuroprosthetic devices.

Noise characterization of a pulse train generated by actively mode-locked lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eliyahu, D.; Salvatore, R.A.; Yariv, A.

1996-07-01

We analyze the entire power spectrum of pulse trains generated by a continuously operating actively mode-locked laser in the presence of noise. We consider the effect of amplitude, pulse-shape, and timing-jitter fluctuations that are characterized by stationary processes. Effects of correlations between different parameters of these fluctuations are studied also. The nonstationary timing-jitter fluctuations of passively mode-locked lasers and their influence on the power spectrum is discussed as well. {copyright} {ital 1996 Optical Society of America.}

Characterizing the parameters of ultra-short optical dissipative solitary pulses in the actively mode-locked semiconductor laser with an external fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Campos Acosta, Joaquin; Moreno Zarate, Pedro; Mansurova, Svetlana; Il'in, Yurij V.; Tarasov, Il'ya S.

2010-06-01

We discuss specifically elaborated approach for characterizing the train-average parameters of low-power picosecond optical pulses with the frequency chirp, arranged in high-repetition-frequency trains, in both time and frequency domains. This approach had been previously applied to rather important case of pulse generation when a single-mode semiconductor heterolaser operates in a multi-pulse regime of the active mode-locking with an external single-mode fiber cavity. In fact, the trains of optical dissipative solitary pulses, which appear under a double balance between mutually compensating actions of dispersion and nonlinearity as well as gain and optical losses, are under characterization. However, in the contrast with the previous studies, now we touch an opportunity of describing two chirped optical pulses together. The main reason of involving just a pair of pulses is caused by the simplest opportunity for simulating the properties of just a sequence of pulses rather then an isolated pulse. However, this step leads to a set of specific difficulty inherent generally in applying joint time-frequency distributions to groups of signals and consisting in manifestation of various false signals or artefacts. This is why the joint Chio-Williams time-frequency distribution and the technique of smoothing are under preliminary consideration here.

Seasonal migrations of North Atlantic minke whales: novel insights from large-scale passive acoustic monitoring networks.

PubMed

Risch, Denise; Castellote, Manuel; Clark, Christopher W; Davis, Genevieve E; Dugan, Peter J; Hodge, Lynne Ew; Kumar, Anurag; Lucke, Klaus; Mellinger, David K; Nieukirk, Sharon L; Popescu, Cristian Marian; Ramp, Christian; Read, Andrew J; Rice, Aaron N; Silva, Monica A; Siebert, Ursula; Stafford, Kathleen M; Verdaat, Hans; Van Parijs, Sofie M

2014-01-01

Little is known about migration patterns and seasonal distribution away from coastal summer feeding habitats of many pelagic baleen whales. Recently, large-scale passive acoustic monitoring networks have become available to explore migration patterns and identify critical habitats of these species. North Atlantic minke whales (Balaenoptera acutorostrata) perform seasonal migrations between high latitude summer feeding and low latitude winter breeding grounds. While the distribution and abundance of the species has been studied across their summer range, data on migration and winter habitat are virtually missing. Acoustic recordings, from 16 different sites from across the North Atlantic, were analyzed to examine the seasonal and geographic variation in minke whale pulse train occurrence, infer information about migration routes and timing, and to identify possible winter habitats. Acoustic detections show that minke whales leave their winter grounds south of 30° N from March through early April. On their southward migration in autumn, minke whales leave waters north of 40° N from mid-October through early November. In the western North Atlantic spring migrants appear to track the warmer waters of the Gulf Stream along the continental shelf, while whales travel farther offshore in autumn. Abundant detections were found off the southeastern US and the Caribbean during winter. Minke whale pulse trains showed evidence of geographic variation, with longer pulse trains recorded south of 40° N. Very few pulse trains were recorded during summer in any of the datasets. This study highlights the feasibility of using acoustic monitoring networks to explore migration patterns of pelagic marine mammals. Results confirm the presence of minke whales off the southeastern US and the Caribbean during winter months. The absence of pulse train detections during summer suggests either that minke whales switch their vocal behaviour at this time of year, are absent from available recording sites or that variation in signal structure influenced automated detection. Alternatively, if pulse trains are produced in a reproductive context by males, these data may indicate their absence from the selected recording sites. Evidence of geographic variation in pulse train duration suggests different behavioural functions or use of these calls at different latitudes.

Predicting the threshold of pulse-train electrical stimuli using a stochastic auditory nerve model: the effects of stimulus noise.

PubMed

Xu, Yifang; Collins, Leslie M

2004-04-01

The incorporation of low levels of noise into an electrical stimulus has been shown to improve auditory thresholds in some human subjects (Zeng et al., 2000). In this paper, thresholds for noise-modulated pulse-train stimuli are predicted utilizing a stochastic neural-behavioral model of ensemble fiber responses to bi-phasic stimuli. The neural refractory effect is described using a Markov model for a noise-free pulse-train stimulus and a closed-form solution for the steady-state neural response is provided. For noise-modulated pulse-train stimuli, a recursive method using the conditional probability is utilized to track the neural responses to each successive pulse. A neural spike count rule has been presented for both threshold and intensity discrimination under the assumption that auditory perception occurs via integration over a relatively long time period (Bruce et al., 1999). An alternative approach originates from the hypothesis of the multilook model (Viemeister and Wakefield, 1991), which argues that auditory perception is based on several shorter time integrations and may suggest an NofM model for prediction of pulse-train threshold. This motivates analyzing the neural response to each individual pulse within a pulse train, which is considered to be the brief look. A logarithmic rule is hypothesized for pulse-train threshold. Predictions from the multilook model are shown to match trends in psychophysical data for noise-free stimuli that are not always matched by the long-time integration rule. Theoretical predictions indicate that threshold decreases as noise variance increases. Theoretical models of the neural response to pulse-train stimuli not only reduce calculational overhead but also facilitate utilization of signal detection theory and are easily extended to multichannel psychophysical tasks.

Steering population transfer of the Na2 molecule by an ultrashort pulse train

NASA Astrophysics Data System (ADS)

Niu, Dong-Hua; Wang, Shuo; Zhan, Wei-Shen; Tao, Hong-Cai; Wang, Si-Qi

2018-05-01

We theoretically investigate the complete population transfer among quantum states of the Na2 molecule using ultrashort pulse trains using the time-dependent wave packet method. The population accumulation of the target state can be steered by controlling the laser parameters, such as the variable pulse pairs, the different pulse widths, the time delays and the repetition period between two contiguous pulses; in particular, the pulse pairs and the pulse widths have a great effect on the population transfer. The calculations show that the ultrashort pulse train is a feasible solution, which can steer the population transfer from the initial state to the target state efficiently with lower peak intensities.

Cognitive-Behavioral Therapy versus Temporal Pulse Amplitude Biofeedback Training for Recurrent Headache

ERIC Educational Resources Information Center

Martin, Paul R.; Forsyth, Michael R.; Reece, John

2007-01-01

Sixty-four headache sufferers were allocated randomly to cognitive-behavioral therapy (CBT), temporal pulse amplitude (TPA) biofeedback training, or waiting-list control. Fifty-one participants (14M/37F) completed the study, 30 with migraine and 21 with tension-type headache. Treatment consisted of 8, 1-hour sessions. CBT was highly effective,…

Pulse-train Stimulation of Primary Somatosensory Cortex Blocks Pain Perception in Tail Clip Test

PubMed Central

Lee, Soohyun; Hwang, Eunjin; Lee, Dongmyeong

2017-01-01

Human studies of brain stimulation have demonstrated modulatory effects on the perception of pain. However, whether the primary somatosensory cortical activity is associated with antinociceptive responses remains unknown. Therefore, we examined the antinociceptive effects of neuronal activity evoked by optogenetic stimulation of primary somatosensory cortex. Optogenetic transgenic mice were subjected to continuous or pulse-train optogenetic stimulation of the primary somatosensory cortex at frequencies of 15, 30, and 40 Hz, during a tail clip test. Reaction time was measured using a digital high-speed video camera. Pulse-train optogenetic stimulation of primary somatosensory cortex showed a delayed pain response with respect to a tail clip, whereas no significant change in reaction time was observed with continuous stimulation. In response to the pulse-train stimulation, video monitoring and local field potential recording revealed associated paw movement and sensorimotor rhythms, respectively. Our results show that optogenetic stimulation of primary somatosensory cortex at beta and gamma frequencies blocks transmission of pain signals in tail clip test. PMID:28442945

Mechanism for optimization of signal-to-noise ratio of dopamine release based on short-term bidirectional plasticity.

PubMed

Da Cunha, Claudio; McKimm, Eric; Da Cunha, Rafael M; Boschen, Suelen L; Redgrave, Peter; Blaha, Charles D

2017-07-15

Repeated electrical stimulation of dopamine (dopamine) fibers can cause variable effects on further dopamine release; sometimes there are short-term decreases while in other cases short-term increases have been reported. Previous studies have failed to discover what factors determine in which way dopamine neurons will respond to repeated stimulation. The aim of the present study was therefore to investigate what determines the direction and magnitude of this particular form of short-term plasticity. Fixed potential amperometry was used to measure dopamine release in the nucleus accumbens in response to two trains of electrical pulses administered to the ventral tegmental area of anesthetized mice. When the pulse trains were of equal magnitude we found that low magnitude stimulation was associated with short-term suppression and high magnitude stimulation with short-term facilitation of dopamine release. Secondly, we found that the magnitude of the second pulse train was critical for determining the sign of the plasticity (suppression or facilitation), while the magnitude of the first pulse train determined the extent to which the response to the second train was suppressed or facilitated. This form of bidirectional plasticity might provide a mechanism to enhance signal-to-noise ratio of dopamine neurotransmission. Copyright © 2017 Elsevier B.V. All rights reserved.

Temporal femtosecond pulse shaping dependence of laser-induced periodic surface structures in fused silica

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Xuesong; Jiang, Lan; Li, Xin, E-mail: lixin02@bit.edu.cn

2014-07-21

The dependence of periodic structures and ablated areas on temporal pulse shaping is studied upon irradiation of fused silica by femtosecond laser triple-pulse trains. Three types of periodic structures can be obtained by using pulse trains with designed pulse delays, in which the three-dimensional nanopillar arrays with ∼100–150 nm diameters and ∼200 nm heights are first fabricated in one step. These nanopillars arise from the break of the ridges of ripples in the upper portion, which is caused by the split of orthogonal ripples in the bottom part. The localized transient electron dynamics and corresponding material properties are considered for the morphologicalmore » observations.« less

Slow and fast light via SBS in optical fibers for short pulses and broadband pump

NASA Astrophysics Data System (ADS)

Kalosha, V. P.; Chen, Liang; Bao, Xiaoyi

2006-12-01

Slow-light effect via stimulated Brillouin scattering (SBS) in single-mode optical fibers was considered for short probe pulses of nanosecond duration relevant to Gb/s data streams. Unlike recent estimations of delay versus pump based on steady-state small-signal approximation we have used numerical solution of three-wave equations describing SBS for a realistic fiber length. Both regimes of small signal and pump depletion (gain saturation) were considered. The physical origin of Stokes pulse distortion is revealed which is related to excitation of long-living acoustic field behind the pulse and prevents effective delay control by pump power increase at cw pumping. We have shown different slope of the gain-dependent delay for different pulse durations. Spectrally broadened pumping by multiple cw components, frequency-modulated pump and pulse train were studied for short pulses which allow to obtain large delay and suppress pulse distortion. In the pump-depletion regime of pumping by pulse train, both pulse delay and distortion decrease with increasing pump, and the pulse achieves advancement.

Self-stimulation in the rat: quantitative characteristics of the reward pathway.

PubMed

Gallistel, C R

1978-12-01

Quantitative characteristics of the neural pathway that carries the reinforcing signal in electrical self-stimulation of the brain were established by finding which combinations of stimulation parameters give the same performance in a runway. The reward for each run was a train of evenly spaced monophasic cathodal pulses from a monopolar electrode. With train duration and pulse frequency held constant, the required current was a hyperbolic function of pulse duration, with chronaxie c approximately 1.5 msec. With pulse duration held constant, the required strength of the train (the charge delivered per second) was a hyperbolic function of train duration, with chronaxie C approximately 500 msec. To a first approximation, the values of c and C were independent of the choice either of train duration and pulse frequency or of pulse duration, respectively. Hence, the current intensity required by any choice of train duration, pulse frequency, and pulse duration dependent on only two basic parameters, c and C, and one quantity, Qi, the required impulse charge. These may reflect, respectively, current integration by directly excited neurons; temporal integration of neural activity by synaptic processes in a neural network; and the peak of the impulse response of the network, assuming that the network has linear dynamics and that the reward depends on the peak of the output of the network.

Ultrashort-pulse-train pump and dump excitation of a diatomic molecule

NASA Astrophysics Data System (ADS)

de Araujo, Luís E. E.

2010-09-01

An excitation scheme is proposed for transferring population between ground-vibrational levels of a molecule. The transfer is accomplished by pumping and dumping population with a pair of coherent ultrashort-pulse trains via a stationary state. By mismatching the teeth of the frequency combs associated with the pulse trains to the vibrational levels, high selectivity in the excitation, along with high transfer efficiency, is predicted. The pump-dump scheme does not suffer from spontaneous emission losses, it is insensitive to the pump-dump-train delay, and it requires only basic pulse shaping.

Ultrashort-pulse-train pump and dump excitation of a diatomic molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araujo, Luis E. E. de

An excitation scheme is proposed for transferring population between ground-vibrational levels of a molecule. The transfer is accomplished by pumping and dumping population with a pair of coherent ultrashort-pulse trains via a stationary state. By mismatching the teeth of the frequency combs associated with the pulse trains to the vibrational levels, high selectivity in the excitation, along with high transfer efficiency, is predicted. The pump-dump scheme does not suffer from spontaneous emission losses, it is insensitive to the pump-dump-train delay, and it requires only basic pulse shaping.

Noise tolerance in wavelength-selective switching of optical differential quadrature-phase-shift-keying pulse train by collinear acousto-optic devices.

PubMed

Goto, Nobuo; Miyazaki, Yasumitsu

2014-06-01

Optical switching of high-bit-rate quadrature-phase-shift-keying (QPSK) pulse trains using collinear acousto-optic (AO) devices is theoretically discussed. Since the collinear AO devices have wavelength selectivity, the switched optical pulse trains suffer from distortion when the bandwidth of the pulse train is comparable to the pass bandwidth of the AO device. As the AO device, a sidelobe-suppressed device with a tapered surface-acoustic-wave (SAW) waveguide and a Butterworth-type filter device with a lossy SAW directional coupler are considered. Phase distortion of optical pulse trains at 40 to 100  Gsymbols/s in QPSK format is numerically analyzed. Bit-error-rate performance with additive Gaussian noise is also evaluated by the Monte Carlo method.

Virtual Active Touch Using Randomly Patterned Intracortical Microstimulation

PubMed Central

O’Doherty, Joseph E.; Lebedev, Mikhail A.; Li, Zheng; Nicolelis, Miguel A.L.

2012-01-01

Intracortical microstimulation (ICMS) has promise as a means for delivering somatosensory feedback in neuroprosthetic systems. Various tactile sensations could be encoded by temporal, spatial, or spatiotemporal patterns of ICMS. However, the applicability of temporal patterns of ICMS to artificial tactile sensation during active exploration is unknown, as is the minimum discriminable difference between temporally modulated ICMS patterns. We trained rhesus monkeys in an active exploration task in which they discriminated periodic pulse-trains of ICMS (200 Hz bursts at a 10 Hz secondary frequency) from pulse trains with the same average pulse rate, but distorted periodicity (200 Hz bursts at a variable instantaneous secondary frequency). The statistics of the aperiodic pulse trains were drawn from a gamma distribution with mean inter-burst intervals equal to those of the periodic pulse trains. The monkeys distinguished periodic pulse trains from aperiodic pulse trains with coefficients of variation 0.25 or greater. Reconstruction of movement kinematics, extracted from the activity of neuronal populations recorded in the sensorimotor cortex concurrent with the delivery of ICMS feedback, improved when the recording intervals affected by ICMS artifacts were removed from analysis. These results add to the growing evidence that temporally patterned ICMS can be used to simulate a tactile sense for neuroprosthetic devices. PMID:22207642

Simple and robust generation of ultrafast laser pulse trains using polarization-independent parallel-aligned thin films

NASA Astrophysics Data System (ADS)

Wang, Andong; Jiang, Lan; Li, Xiaowei; Wang, Zhi; Du, Kun; Lu, Yongfeng

2018-05-01

Ultrafast laser pulse temporal shaping has been widely applied in various important applications such as laser materials processing, coherent control of chemical reactions, and ultrafast imaging. However, temporal pulse shaping has been limited to only-in-lab technique due to the high cost, low damage threshold, and polarization dependence. Herein we propose a novel design of ultrafast laser pulse train generation device, which consists of multiple polarization-independent parallel-aligned thin films. Various pulse trains with controllable temporal profile can be generated flexibly by multi-reflections within the splitting films. Compared with other pulse train generation techniques, this method has advantages of compact structure, low cost, high damage threshold and polarization independence. These advantages endow it with high potential for broad utilization in ultrafast applications.

Enhancement cavities for zero-offset-frequency pulse trains.

PubMed

Holzberger, S; Lilienfein, N; Trubetskov, M; Carstens, H; Lücking, F; Pervak, V; Krausz, F; Pupeza, I

2015-05-15

The optimal enhancement of broadband optical pulses in a passive resonator requires a seeding pulse train with a specific carrier-envelope-offset frequency. Here, we control the phase of the cavity mirrors to tune the offset frequency for which a given comb is optimally enhanced. This enables the enhancement of a zero-offset-frequency train of sub-30-fs pulses to multi-kW average powers. The combination of pulse duration, power, and zero phase slip constitutes a crucial step toward the generation of attosecond pulses at multi-10-MHz repetition rates. In addition, this control affords the enhancement of pulses generated by difference-frequency mixing, e.g., for mid-infrared spectroscopy.

DCL System Using Deep Learning Approaches for Land-Based or Ship-Based Real-Time Recognition and Localization of Marine Mammals

DTIC Science & Technology

2013-09-30

method has been successfully implemented to automatically detect and recognize pulse trains from minke whales ( songs ) and sperm whales (Physeter...workshops, conferences and data challenges 2. Enhancements of the ASR algorithm for frequency-modulated sounds: Right Whale Study 3...Enhancements of the ASR algorithm for pulse trains: Minke Whale Study 4. Mining Big Data Sound Archives using High Performance Computing software and hardware

Power pulsing of the CMOS sensor Mimosa 26

NASA Astrophysics Data System (ADS)

Kuprash, Oleg

2013-12-01

Mimosa 26 is a monolithic active pixel sensor developed by IPHC (Strasbourg) & IRFU (Saclay) as a prototype for the ILC vertex detector studies. The resolution requirements for the ILC tracking detector are very extreme, demanding very low material in the detector, thus only air cooling can be considered. Power consumption has to be reduced as far as possible. The beam structure of the ILC allows the possibility of power pulsing: only for about the 1 ms long bunch train full power is required, and during the 199 ms long pauses between the bunch trains the power can be reduced to a minimum. Not being adapted for the power pulsing, the sensor shows in laboratory tests a good performance under power pulsing. The power pulsing allows to significantly reduce the heating of the chip and divides power consumption approximately by a factor of 6. In this report a summary of power pulsing studies using the digital readout of Mimosa 26 is given.

Can YAG screen accept LEReC bunch train?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seletskiy, S.; Thieberger, P.; Miller, T.

2016-05-18

LEReC RF diagnostic beamline is supposed to accept 250 us long pulse trains of 1.6 MeV – 2.6 MeV (kinetic energy) electrons. This beamline is equipped with YAG profile monitor. Since we are interested in observing only the last macro bunch in the train, one of the possibilities is to install a fast kicker and a dedicated dump upstream of the YAG screen (and related diagnostics equipment). This approach is expensive and challenging from engineering point of view. Another possibility is to send the whole pulse train to the YAG screen and to use a fast gated camera (such asmore » Imperex B0610 with trigger jitter under 60ns) to observe the image from the last pulse only. In this paper we study the feasibility of the last approach.« less

Characterizing the graded structure of false killer whale (Pseudorca crassidens) vocalizations.

PubMed

Murray, S O; Mercado, E; Roitblat, H L

1998-09-01

The vocalizations from two, captive false killer whales (Pseudorca crassidens) were analyzed. The structure of the vocalizations was best modeled as lying along a continuum with trains of discrete, exponentially damped sinusoidal pulses at one end and continuous sinusoidal signals at the other end. Pulse trains were graded as a function of the interval between pulses where the minimum interval between pulses could be zero milliseconds. The transition from a pulse train with no inter-pulse interval to a whistle could be modeled by gradations in the degree of damping. There were many examples of vocalizations that were gradually modulated from pulse trains to whistles. There were also vocalizations that showed rapid shifts in signal type--for example, switching immediately from a whistle to a pulse train. These data have implications when considering both the possible function(s) of the vocalizations and the potential sound production mechanism(s). A short-time duty cycle measure was developed to characterize the graded structure of the vocalizations. A random sample of 500 vocalizations was characterized by combining the duty cycle measure with peak frequency measurements. The analysis method proved to be an effective metric for describing the graded structure of false killer whale vocalizations.

Self-stabilizing optical clock pulse-train generator using SOA and saturable absorber for asynchronous optical packet processing.

PubMed

Nakahara, Tatsushi; Takahashi, Ryo

2013-05-06

We propose a novel, self-stabilizing optical clock pulse-train generator for processing preamble-free, asynchronous optical packets with variable lengths. The generator is based on an optical loop that includes a semiconductor optical amplifier (SOA) and a high-extinction spin-polarized saturable absorber (SA), with the loop being self-stabilized by balancing out the gain and absorption provided by the SOA and SA, respectively. The optical pulse train is generated by tapping out a small portion of a circulating seed pulse. The convergence of the generated pulse energy is enabled by the loop round-trip gain function that has a negative slope due to gain saturation in the SOA. The amplified spontaneous emission (ASE) of the SOA is effectively suppressed by the SA, and a backward optical pulse launched into the SOA enables overcoming the carrier-recovery speed mismatch between the SOA and SA. Without external control for the loop gain, a stable optical pulse train consisting of more than 50 pulses with low jitter is generated from a single 10-ps seed optical pulse even with a variation of 10 dB in the seed pulse intensity.

Training Effects of Alternated and Pulsed Currents on the Quadriceps Muscles of Athletes.

PubMed

Oliveira, Pedro; Modesto, Karenina Arrais Guida; Bottaro, Martim; Babault, Nicolas; Durigan, João Luiz Quagliotti

2018-05-22

The aim of the study was to evaluate the effects of 6 weeks training with different neuromuscular electrical stimulation (NMES) currents (medium alternated and low-frequency pulsed current) on muscle architecture and neuromuscular performance of competitive athletes. A double-blind controlled and randomized experimental study was carried out with 33 athletes (22.2±2.6 yrs, 74.7±9.8 kg, 176.8±6.0 cm), divided into 3 groups: mid-frequency current (MF, n=12), pulsed current (PC, n=11) and the control group (CG, n=10). Quadriceps maximal voluntary peak torque (PT) and corresponding vastus lateralis electromyographic activity, evoked torque (PT-NMES), vastus lateralis muscle thickness, fascicle length, pennation angle, and level of discomfort were assessed before and after the interventions. NMES training was performed 3 times per week and consisted of 18 sessions, 15 min/session, 6 s duration in each contraction interspersed with 18 s rest. After the training period, muscle thickness increased in the MF and PC groups (p<0.05). PT-NMES increased only in the PC group (p<0.05). All currents produced similar levels of discomfort (p>0.05). Quadriceps NMES training applied through alternated or pulsed currents produced similar effects in architecture and neuromuscular performance in competitive athletes. © Georg Thieme Verlag KG Stuttgart · New York.

Directly driven source of multi-gigahertz, sub-picosecond optical pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messerly, Michael J.; Dawson, Jay W.; Barty, Christopher P.J.

2015-10-20

A robust, compact optical pulse train source is described, with the capability of generating sub-picosecond micro-pulse sequences, which can be periodic as well as non-periodic, and at repetition rates tunable over decades of baseline frequencies, from MHz to multi-GHz regimes. The micro-pulses can be precisely controlled and formatted to be in the range of many ps in duration to as short as several fs in duration. The system output can be comprised of a continuous wave train of optical micro-pulses or can be programmed to provide gated bursts of macro-pulses, with each macro-pulse consisting of a specific number of micro-pulsesmore » or a single pulse picked from the higher frequency train at a repetition rate lower than the baseline frequency. These pulses could then be amplified in energy anywhere from the nJ to MJ range.« less

A direct temporal domain approach for ultrafast optical signal processing and its implementation using planar lightwave circuits

NASA Astrophysics Data System (ADS)

Xia, Bing

Ultrafast optical signal processing, which shares the same fundamental principles of electrical signal processing, can realize numerous important functionalities required in both academic research and industry. Due to the extremely fast processing speed, all-optical signal processing and pulse shaping have been widely used in ultrafast telecommunication networks, photonically-assisted RFlmicro-meter waveform generation, microscopy, biophotonics, and studies on transient and nonlinear properties of atoms and molecules. In this thesis, we investigate two types of optical spectrally-periodic (SP) filters that can be fabricated on planar lightwave circuits (PLC) to perform pulse repetition rate multiplication (PRRM) and arbitrary optical waveform generation (AOWG). First, we present a direct temporal domain approach for PRRM using SP filters. We show that the repetition rate of an input pulse train can be multiplied by a factor N using an optical filter with a free spectral range that does not need to be constrained to an integer multiple of N. Furthermore, the amplitude of each individual output pulse can be manipulated separately to form an arbitrary envelope at the output by optimizing the impulse response of the filter. Next, we use lattice-form Mach-Zehnder interferometers (LF-MZI) to implement the temporal domain approach for PRRM. The simulation results show that PRRM with uniform profiles, binary-code profiles and triangular profiles can be achieved. Three silica based LF-MZIs are designed and fabricated, which incorporate multi-mode interference (MMI) couplers and phase shifters. The experimental results show that 40 GHz pulse trains with a uniform envelope pattern, a binary code pattern "1011" and a binary code pattern "1101" are generated from a 10 GHz input pulse train. Finally, we investigate 2D ring resonator arrays (RRA) for ultraf ast optical signal processing. We design 2D RRAs to generate a pair of pulse trains with different binary-code patterns simultaneously from a single pulse train at a low repetition rate. We also design 2D RRAs for AOWG using the modified direct temporal domain approach. To demonstrate the approach, we provide numerical examples to illustrate the generation of two very different waveforms (square waveform and triangular waveform) from the same hyperbolic secant input pulse train. This powerful technique based on SP filters can be very useful for ultrafast optical signal processing and pulse shaping.

Molecular spinning by a chiral train of short laser pulses

NASA Astrophysics Data System (ADS)

Floß, Johannes; Averbukh, Ilya Sh.

2012-12-01

We provide a detailed theoretical analysis of molecular rotational excitation by a chiral pulse train, a sequence of linearly polarized pulses with the polarization direction rotating from pulse to pulse by a controllable angle. Molecular rotation with a preferential rotational sense (clockwise or counterclockwise) can be excited by this scheme. We show that the directionality of the rotation is caused by quantum interference of different excitation pathways. The chiral pulse train is capable of selective excitation of molecular isotopologs and nuclear spin isomers in a mixture. We demonstrate this using 14N2 and 15N2 as examples for isotopologs and para- and ortho-nitrogen as examples for nuclear-spin isomers.

Gigahertz repetition rate, sub-femtosecond timing jitter optical pulse train directly generated from a mode-locked Yb:KYW laser.

PubMed

Yang, Heewon; Kim, Hyoji; Shin, Junho; Kim, Chur; Choi, Sun Young; Kim, Guang-Hoon; Rotermund, Fabian; Kim, Jungwon

2014-01-01

We show that a 1.13 GHz repetition rate optical pulse train with 0.70 fs high-frequency timing jitter (integration bandwidth of 17.5 kHz-10 MHz, where the measurement instrument-limited noise floor contributes 0.41 fs in 10 MHz bandwidth) can be directly generated from a free-running, single-mode diode-pumped Yb:KYW laser mode-locked by single-wall carbon nanotube-coated mirrors. To our knowledge, this is the lowest-timing-jitter optical pulse train with gigahertz repetition rate ever measured. If this pulse train is used for direct sampling of 565 MHz signals (Nyquist frequency of the pulse train), the jitter level demonstrated would correspond to the projected effective-number-of-bit of 17.8, which is much higher than the thermal noise limit of 50 Ω load resistance (~14 bits).

Observations of double layer-like and soliton-like structures in the ionosphere

NASA Technical Reports Server (NTRS)

Boehm, M. H.; Carlson, C. W.; Mcfadden, J.; Mozer, F. S.

1984-01-01

Two types of large electric field signatures, individual pulses and pulse trains, were observed on a sounding rocket launched into the afternoon auroral zone on January 21, 1982. The typical electric fields in the individual pulses were 50 mV/m or larger, aligned mostly parallel to B, and the corresponding potentials were at leat 100 mV (kT approximately 0.3 eV). A lower limit of 15 km/sec can be set on the velocity of these structures, indicating that they were not ion acoustic double layers. The pulse trains, each consisting of on the order of 100 pulses, were observed in close association with intense plasma frequency waves. This correlation is consistent with the interpretation of these trains as Langmuir solitons. The pulse trains correlate better with the intensity of the field-aligned currents than with the energetic electron flux.

Antiemesis effect and brain fMRI response of gastric electrical stimulation with different parameters in dogs.

PubMed

Yu, X; Tu, L; Lei, P; Song, J; Xu, H; Hou, X

2014-07-01

The aims of this study were to investigate the effect of gastric electrical stimulation (GES) with different parameters on emesis induced by apomorphine, and possible center mechanisms by brain functional magnetic resonance imaging (fMRI). Six dogs implanted with electrodes on gastric serosa were used in this study. Part 1: Apomorphine was injected in the control session and GES sessions. GESs with different parameters were applied in GES session. Gastric slow waves and emesis and behaviors suggestive of nausea were recorded in each session. Part 2: Each dog was anesthetized and given GESs with different parameters or sham stimulation for 15 min after baseline (5 min), respectively. The location of cerebral activation induced by GES was investigated by fMRI. Apomorphine induced emesis and behaviors suggestive of nausea, and gastric dysrhythmia. The emesis frequency in control session was 5.5 ± 0.99, and symptoms score was 22.17 ± 1.01. GES with short pulse and long pulse could not improve emesis and symptoms induced by apomorphine. The emesis frequency (4.5 ± 0.76 in short pulse and 6.33 ± 1.05 in long pulse) and symptoms scores had no significant difference compared to control session (each p > 0.05). GES with trains of short pulse reduced emesis time frequency (3.83 ± 0.7, p = 0.042 vs control) and symptoms score (p = 0.037 vs control) obviously. Brain fMRI showed that GES with short pulse and long pulse activated brain stem region, and trains of short pulse made amygdala and occipital lobe activation. Apomorphine induced emesis and gastric dysrhythmia. GES with trains of short pulses relieves emetic responses through activation of amygdala region. © 2014 John Wiley & Sons Ltd.

Effects of high-level pulse train stimulation on retinal function.

PubMed

Cohen, Ethan D

2009-06-01

We examined how stimulation of the local retina by high-level current pulse trains affected the light-evoked responses of the retinal ganglion cells. The spikes of retinal ganglion cell axons were recorded extracellularly using an in vitro eyecup preparation of the rabbit retina. Epiretinal electrical stimulation was delivered via a 500 microm inner diameter saline-filled, transparent tube positioned over the retinal surface forming the receptive field center. Spot stimuli were presented periodically to the receptive field center during the experiment. Trains of biphasic 1 ms current pulses were delivered to the retina at 50 Hz for 1 min. Pulse train charge densities of 1.3-442 microC/cm(2)/phase were examined. After pulse train stimulation with currents >or=300 microA (133 microC/cm(2)/phase), the ganglion cell's ability to respond to light was depressed and a significant time was required for recovery of the light-evoked response. During train stimulation, the ganglion cell's ability to spike following each current pulse fatigued. The current levels evoking train-evoked depression were suprathreshold to those evoking action potentials. Train-evoked depression was stronger touching the retinal surface, and in some cases impaired ganglion cell function for up to 30 min. This overstimulation could cause a transient refractory period for electrically stimulated perception in the retinal region below the electrode.

Regression analysis of radial artery pulse palpation as a potential tool for traditional Chinese medicine training education.

PubMed

Huang, Po-Yu; Lin, Wen-Chen; Chiu, Bill Yuan-Chi; Chang, Hen-Hong; Lin, Kang-Ping

2013-12-01

Pulse palpation was an important part of the traditional Chinese medicine (TCM) vascular examination. It is challenging for new physicians to learn to differentiate between palpations of various pulse types, due to limited comparative learning time with established masters, and so normally it takes many years to master the art. The purpose of this study was to introduce an offline TCM skill evaluation and comparison system that makes available learning of palpation without the master's presence. We record patient's radial artery pulse using an existing pressure-based pulse acquisition system, then annotate it with teachers' evaluation when palpating the same patient, assigned as likelihood of it being each pulse type, e.g. wiry, slippery, hesitant. These training data were separated into per-doctor and per-skill databases for evaluation and comparison purposes, using the following novel procedure: each database was used as training data to a panel of time-series data-mining algorithms, driven by two validation tests, with the created training models evaluated in mean-squared-error. Each validation of the panel and training data yielded an array of error terms, and we chose one to quantitatively evaluate palpation techniques, giving way to compute self consistency and mutual-similarity across different practitioners and techniques. Our experiment of two practitioners and 396 per-processing samples yielded the following: one of the physicians has much higher value of self-consistency for all tested pulse types. Also, the two physicians have high similarity in how they palpate the slipper pulse (P) type, but very dissimilar for hesitant (H) type. This system of skill comparisons may be more broadly applied in places where supervised learning algorithms can detect and use meaningful features in the data; we chose a panel of algorithms previously shown to be effective for many time-series types, but specialized algorithms may be added to improve feature-specific aspect of evaluation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Laser induced periodic surface structuring on Si by temporal shaped femtosecond pulses.

PubMed

Almeida, G F B; Martins, R J; Otuka, A J G; Siqueira, J P; Mendonca, C R

2015-10-19

We investigated the effect of temporal shaped femtosecond pulses on silicon laser micromachining. By using sinusoidal spectral phases, pulse trains composed of sub-pulses with distinct temporal separations were generated and applied to the silicon surface to produce Laser Induced Periodic Surface Structures (LIPSS). The LIPSS obtained with different sub-pulse separation were analyzed by comparing the intensity of the two-dimensional fast Fourier Transform (2D-FFT) of the AFM images of the ripples (LIPSS). It was observed that LIPSS amplitude is more emphasized for the pulse train with sub-pulses separation of 128 fs, even when compared with the Fourier transform limited pulse. By estimating the carrier density achieved at the end of each pulse train, we have been able to interpret our results with the Sipe-Drude model, that predicts that LIPSS efficacy is higher for a specific induced carrier density. Hence, our results indicate that temporal shaping of the excitation pulse, performed by spectral phase modulation, can be explored in fs-laser microstructuring.

Method and device for measuring single-shot transient signals

DOEpatents

Yin, Yan

2004-05-18

Methods, apparatus, and systems, including computer program products, implementing and using techniques for measuring multi-channel single-shot transient signals. A signal acquisition unit receives one or more single-shot pulses from a multi-channel source. An optical-fiber recirculating loop reproduces the one or more received single-shot optical pulses to form a first multi-channel pulse train for circulation in the recirculating loop, and a second multi-channel pulse train for display on a display device. The optical-fiber recirculating loop also optically amplifies the first circulating pulse train to compensate for signal losses and performs optical multi-channel noise filtration.

Reaction time to changes in the tempo of acoustic pulse trains.

NASA Technical Reports Server (NTRS)

Smith, R. P.; Warm, J. S.; Westendorf, D. H.

1973-01-01

Investigation of the ability of human observers to detect accelerations and decelerations in the rate of presentation of pulsed stimuli, i.e., changes in the tempo of acoustic pulse trains. Response times to accelerations in tempo were faster than to decelerations. Overall speed of response was inversely related to the pulse repetition rate.

Variation in male courtship song traits in Drosophila virilis: the effects of selection and drift on song divergence at the intraspecific level.

PubMed

Huttunen, Susanna; Aspi, Jouni; Schlötterer, Christian; Routtu, Jarkko; Hoikkala, Anneli

2008-01-01

Genetic and phenotypic divergence of Drosophila virilis laboratory strains originating from different parts of the species range were studied with the aid of microsatellite markers and by analysing male courtship songs. The strains from America, Europe, continental Asia and Japan showed moderate geographic clustering both at the genetic level and in several traits of the male song. The genetic distances and the song divergence of the strains did not show significant association, which suggests that the songs have not diverged solely as a side-effect of genetic divergence. Comparison of the songs of the laboratory strains to those of freshly collected strains showed that pulse characters of the song are quite sensitive to culture conditions. While laboratory rearing of the flies had no effect on the number of pulses in a pulse train or the pulse train length, the tendency of the sound pulses to become longer during laboratory maintenance could explain the lack of geographic variation in pulse length and inter pulse interval. Sensitivity of songs to culturing conditions should be taken in account in studies on song divergence.

Impact of a web based interactive simulation game (PULSE) on nursing students' experience and performance in life support training--a pilot study.

PubMed

Cook, Neal F; McAloon, Toni; O'Neill, Philip; Beggs, Richard

2012-08-01

The delivery of effective life support measures is highly associated with the quality, design and implementation of the education that underpins it. Effectively responding to a critical event is a requirement for all nurses illustrating the need for effective educational approaches from pre-registration training through to enhancing and maintaining life support skills after qualification. This paper reports the findings of utilising a web-based multimedia simulation game PULSE (Platform for Undergraduate Life Support Education). The platform was developed to enhance the student experience of life support education, to motivate on-going learning and engagement and to improve psychomotor skills associated with the provision of Intermediate Life Support (ILS) training. Pre training participants played PULSE and during life support training data was collected from an intervention and a control group of final year undergraduate nursing students (N=34). Quantitative analysis of performance took place and qualitative data was generated from a questionnaire assessing the learning experience. A statistically significant difference was found between the competence the groups displayed in the three skills sets of checking equipment, airway assessment and the safe/effective use of defibrillator at ILS level, and PULSE was positively evaluated as an educational tool when used alongside traditional life support training. Copyright © 2011 Elsevier Ltd. All rights reserved.

Mechanical bioeffects of pulsed high intensity focused ultrasound on a simple neural model.

PubMed

Wahab, Radia Abdul; Choi, Mina; Liu, Yunbo; Krauthamer, Victor; Zderic, Vesna; Myers, Matthew R

2012-07-01

To study how pressure pulses affect nerves through mechanisms that are neither thermal nor cavitational, and investigate how the effects are related to cumulative radiation-force impulse (CRFI). Applications include traumatic brain injury and acoustic neuromodulation. A simple neural model consisting of the giant axon of a live earthworm was exposed to trains of pressure pulses produced by an 825 kHz focused ultrasound transducer. The peak negative pressure of the pulses and duty cycle of the pulse train were controlled so that neither cavitation nor significant temperature rise occurred. The amplitude and conduction velocity of action-potentials triggered in the worm were measured as the magnitude of the pulses and number of pulses in the pulse trains were varied. The functionality of the axons decreased when sufficient pulse energy was applied. The level of CRFI at which the observed effects occur is consistent with the lower levels of injury observed in this study relative to blast tubes. The relevant CRFI values are also comparable to CRFI values in other studies showing measureable changes in action-potential amplitudes and velocities. Plotting the measured action-potential amplitudes and conduction velocities from different experiments with widely varying exposure regimens against the single parameter of CRFI yielded values that agreed within 21% in terms of amplitude and 5% in velocity. A predictive model based on the assumption that the temporal rate of decay of action-potential amplitude and velocity is linearly proportional the radiation force experienced by the axon predicted the experimental amplitudes and conduction velocities to within about 20% agreement. The functionality of axons decreased due to noncavitational mechanical effects. The radiation force, possibly by inducing changes in ion-channel permeability, appears to be a possible mechanism for explaining the observed degradation. The CRFI is also a promising parameter for quantifying neural bioeffects during exposure to pressure waves, and for predicting axon functionality.

Effects of Long-term Physical Training on the Bearers of a Float during the Nagasaki Kunchi Festival.

PubMed

Shibata, Shigemori; Kawano, Hiroaki; Maemura, Koji

Objective The Nagasaki Kunchi Festival is one of the most famous festivals in Nagasaki. The bearers the floats that are used in this festival undergo long-term training for the performance. However, there have not been any studies on the effects of this training on the health of the float bearers. Methods Thirty-four men ranging in age from 20 to 49 years (mean age: 35.77.6 years) were included in the study. We examined the following parameters before and after the training: body weight (BW), body mass index (BMI), body fat percentage, muscle volume, systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse rate (PR), pulse pressure (PP), bearing power, arterial pressure volume index (API), and arterial velocity pulse index (AVI). Results For all participants, the BW, BMI, body fat percentage, and PR were significantly decreased, and the muscle volume and bearing power were significantly increased after the training; however, there were no significant changes in the SBP, DBP, PP, API, or AVI. In the participants with hypertension, in addition to decreases in BW, BMI, body fat percentage, PR, and PP, the SBP, DBP, and API were significantly decreased after the training. Conclusion Training for bearing a float during Nagasaki Kunchi effectively improved the body structure of all participants and reduced the BP and API in participants with hypertension.

Effects of Long-term Physical Training on the Bearers of a Float during the Nagasaki Kunchi Festival

PubMed Central

Shibata, Shigemori; Kawano, Hiroaki; Maemura, Koji

2017-01-01

Objective The Nagasaki Kunchi Festival is one of the most famous festivals in Nagasaki. The bearers the floats that are used in this festival undergo long-term training for the performance. However, there have not been any studies on the effects of this training on the health of the float bearers. Methods Thirty-four men ranging in age from 20 to 49 years (mean age: 35.7±7.6 years) were included in the study. We examined the following parameters before and after the training: body weight (BW), body mass index (BMI), body fat percentage, muscle volume, systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse rate (PR), pulse pressure (PP), bearing power, arterial pressure volume index (API), and arterial velocity pulse index (AVI). Results For all participants, the BW, BMI, body fat percentage, and PR were significantly decreased, and the muscle volume and bearing power were significantly increased after the training; however, there were no significant changes in the SBP, DBP, PP, API, or AVI. In the participants with hypertension, in addition to decreases in BW, BMI, body fat percentage, PR, and PP, the SBP, DBP, and API were significantly decreased after the training. Conclusion Training for bearing a float during Nagasaki Kunchi effectively improved the body structure of all participants and reduced the BP and API in participants with hypertension. PMID:28049988

Effects of High-Rate Pulse Trains on Electrode Discrimination in Cochlear Implant Users

PubMed Central

Runge-Samuelson, Christina L.

2009-01-01

Overcoming issues related to abnormally high neural synchrony in response to electrical stimulation is one aspect in improving hearing with a cochlear implant. Desynchronization of electrical stimuli have shown benefits in neural encoding of electrical signals and improvements in psychophysical tasks. In the present study, 10 participants with either CII or HiRes 90k Advanced Bionics devices were tested for the effects of desynchronizing constant-amplitude high-rate (5,000 Hz) pulse trains on electrode discrimination of sinusoidal stimuli (1,000 Hz). When averaged across the sinusoidal dynamic range, overall improvements in electrode discrimination with high-rate pulses were found for 8 of 10 participants. This effect was significant for the group (p = .003). Nonmonotonic patterns of electrode discrimination as a function of sinusoidal stimulation level were observed. By providing additional spectral channels, it is possible that clinical implementation of constant-amplitude high-rate pulse trains in a signal processing strategy may improve performance with the device. PMID:19447763

Radiation from long pulse train electron beams in space plasmas

NASA Technical Reports Server (NTRS)

Harker, K. J.; Banks, P. M.

1985-01-01

A previous study of electromagnetic radiation from a finite train of electron pulses is extended to an infinite train of such pulses. The electrons are assumed to follow an idealized helical path through a space plasma in such a manner as to retain their respective position within the beam. This leads to radiation by coherent spontaneous emission. The waves of interest in this region are the whistler slow (compressional) and fast (torsional) Alfven waves. Although a general theory is developed, analysis is then restricted to two approximations, the short and long electron beam. Formulas for the radiation per unit solid angle from the short beam are presented as a function of both propagation and ray angles, electron beam pulse width and separation and beam current, voltage, and pitch angle. Similar formulas for the total power radiated from the long beam are derived as a function of frequency, propagation angle, and ray angle. Predictions of the power radiated are presented for representative examples as determined by the long beam theory.

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 responses in long-term severely-hearing impaired CI users could be an attribute of processes associated with long-term hearing impairment and/or electrical stimulation. Copyright © 2016 Elsevier B.V. All rights reserved.

Modelling the isometric force response to multiple pulse stimuli in locust skeletal muscle.

PubMed

Wilson, Emma; Rustighi, Emiliano; Mace, Brian R; Newland, Philip L

2011-02-01

An improved model of locust skeletal muscle will inform on the general behaviour of invertebrate and mammalian muscle with the eventual aim of improving biomedical models of human muscles, embracing prosthetic construction and muscle therapy. In this article, the isometric response of the locust hind leg extensor muscle to input pulse trains is investigated. Experimental data was collected by stimulating the muscle directly and measuring the force at the tibia. The responses to constant frequency stimulus trains of various frequencies and number of pulses were decomposed into the response to each individual stimulus. Each individual pulse response was then fitted to a model, it being assumed that the response to each pulse could be approximated as an impulse response and was linear, no assumption were made about the model order. When the interpulse frequency (IPF) was low and the number of pulses in the train small, a second-order model provided a good fit to each pulse. For moderate IPF or for long pulse trains a linear third-order model provided a better fit to the response to each pulse. The fit using a second-order model deteriorated with increasing IPF. When the input comprised higher IPFs with a large number of pulses the assumptions that the response was linear could not be confirmed. A generalised model is also presented. This model is second-order, and contains two nonlinear terms. The model is able to capture the force response to a range of inputs. This includes cases where the input comprised of higher frequency pulse trains and the assumption of quasi-linear behaviour could not be confirmed.

The efficiency of backward magnetic-pulse processing

NASA Astrophysics Data System (ADS)

Kudasov, Yu. B.; Maslov, D. A.; Surdin, O. M.

2017-01-01

The dependence of the efficiency of magnetic-pulse processing of materials on the pulsed magnetic-field shape has been studied. It is shown that, by using a pulse train instead of a single pulse in the fast-rising component of a magnetic field applied during the backward forming process, it is possible to increase the specific mechanical impulse transferred to a workpiece and, thus, improve the efficiency of processing. Possible applications of the proposed method to removing dents from car chassis and aircraft parts are considered

MULTI-CHANNEL PULSE HEIGHT ANALYZER

DOEpatents

Boyer, K.; Johnstone, C.W.

1958-11-25

An improved multi-channel pulse height analyzer of the type where the device translates the amplitude of each pulse into a time duration electrical quantity which is utilized to control the length of a train of pulses forwarded to a scaler is described. The final state of the scaler for any one train of pulses selects the appropriate channel in a magnetic memory in which an additional count of one is placed. The improvement consists of a storage feature for storing a signal pulse so that in many instances when two signal pulses occur in rapid succession, the second pulse is preserved and processed at a later time.

Urgency is a non-monotonic function of pulse rate.

PubMed

Russo, Frank A; Jones, Jeffery A

2007-11-01

Magnitude estimation was used to assess the experience of urgency in pulse-train stimuli (pulsed white noise) ranging from 3.13 to 200 Hz. At low pulse rates, pulses were easily resolved. At high pulse rates, pulses fused together leading to a tonal sensation with a clear pitch level. Urgency ratings followed a nonmonotonic (polynomial) function with local maxima at 17.68 and 200 Hz. The same stimuli were also used in response time and pitch scaling experiments. Response times were negatively correlated with urgency ratings. Pitch scaling results indicated that urgency of pulse trains is mediated by the perceptual constructs of speed and pitch.

Speech analyzer

NASA Technical Reports Server (NTRS)

Lokerson, D. C. (Inventor)

1977-01-01

A speech signal is analyzed by applying the signal to formant filters which derive first, second and third signals respectively representing the frequency of the speech waveform in the first, second and third formants. A first pulse train having approximately a pulse rate representing the average frequency of the first formant is derived; second and third pulse trains having pulse rates respectively representing zero crossings of the second and third formants are derived. The first formant pulse train is derived by establishing N signal level bands, where N is an integer at least equal to two. Adjacent ones of the signal bands have common boundaries, each of which is a predetermined percentage of the peak level of a complete cycle of the speech waveform.

Ponderomotive Generation and Detection of Attosecond Free-Electron Pulse Trains

NASA Astrophysics Data System (ADS)

Kozák, M.; Schönenberger, N.; Hommelhoff, P.

2018-03-01

Atomic motion dynamics during structural changes or chemical reactions have been visualized by pico- and femtosecond pulsed electron beams via ultrafast electron diffraction and microscopy. Imaging the even faster dynamics of electrons in atoms, molecules, and solids requires electron pulses with subfemtosecond durations. We demonstrate here the all-optical generation of trains of attosecond free-electron pulses. The concept is based on the periodic energy modulation of a pulsed electron beam via an inelastic interaction, with the ponderomotive potential of an optical traveling wave generated by two femtosecond laser pulses at different frequencies in vacuum. The subsequent dispersive propagation leads to a compression of the electrons and the formation of ultrashort pulses. The longitudinal phase space evolution of the electrons after compression is mapped by a second phase-locked interaction. The comparison of measured and calculated spectrograms reveals the attosecond temporal structure of the compressed electron pulse trains with individual pulse durations of less than 300 as. This technique can be utilized for tailoring and initial characterization of suboptical-cycle free-electron pulses at high repetition rates for stroboscopic time-resolved experiments with subfemtosecond time resolution.

Fundamental Study of Three-dimensional Fast Spin-echo Imaging with Spoiled Equilibrium Pulse.

PubMed

Ogawa, Masashi; Kaji, Naoto; Tsuchihashi, Toshio

2017-01-01

Three-dimensional fast spin-echo (3D FSE) imaging with variable refocusing flip angle has been recently applied to pre- or post-enhanced T 1 -weighted imaging. To reduce the acquisition time, this sequence requires higher echo train length (ETL), which potentially causes decreased T 1 contrast. Spoiled equilibrium (SpE) pulse consists of a resonant +90° radiofrequency (RF) pulse and is applied at the end of the echo train. This +90° RF pulse brings residual transverse magnetization to the negative longitudinal axis, which makes it possible to increase T 1 contrast. The purpose of our present study was to examine factors that influence the effect of spoiled equilibrium pulse and the relationship between T 1 contrast improvement and imaging parameters and to understand the characteristics of spoiled equilibrium pulse. Phantom studies were conducted using an magnetic resonance imaging (MRI) phantom made of polyvinyl alcohol gel. To evaluate the effect of spoiled equilibrium pulse with changes in repetition time (TR), ETL, and refocusing flip angle, we measured the signal-to-noise ratio and contrast-to-noise ratio (CNR). The effect of spoiled equilibrium pulse was evaluated by calculating the enhancement rate of CNR. The factors that influence the effect of spoiled equilibrium pulse are TR, ETL, and relaxation time of tissues. Spoiled equilibrium pulse is effective with increasing TR and decreasing ETL. The shorter the T 1 value, the better the spoiled equilibrium pulse functions. However, for tissues in which the T 1 value is long (>600 ms), at a TR of 600 ms, improvement in T 1 contrast by applying spoiled equilibrium pulse cannot be expected.

Electrical passivation of nonselective bio molecules in carbon nanotubes: Effect of pulse train in serum

NASA Astrophysics Data System (ADS)

Kim, Seok Hyang; Woo, Jun-Myung; Choi, Seongwook; Park, Young June

2015-06-01

We present an experimental and simulation study about a desorption of albumin, a representative nonselective molecules in serum, on carbon nanotube (CNT) surface as an electrical bio sensing channel under the pulse train condition. The motivation of the study on binding kinetics between CNT surface and albumin is to suppress the adsorption of nonselective proteins in blood such as albumin, thereby enhancing the selectivity of the electrical biosensor. To theoretically model the behavior of molecules and ions under the step pulse bias, the physics on the reaction rate, mass transport, and the resulting surface pH-value are considered using the Poisson and drift-diffusion equations. For the simulation model, the phosphate buffered saline is considered as the electrolyte solution and albumin is considered as a representative charged molecule for nonspecific binding in serum. Both the transient simulation and experimental result indicate that the suppression of the nonspecific binding under the pulse train is due to the unsymmetrical field force experienced by the protein during the pulse transitions (high to low and low to high) and the non-symmetry is caused by the different transient times between the electric field and the charge/discharge of the protein according to the surface pH modulation in serum. The experimental and simulation results clearly indicate that the pulse bias suppresses the nonselective bio molecules adsorption at the CNT surface so that the selectivity of the electrical biosensor for detecting the target molecules can be enhanced.

Multipulsed dynamic moire interferometer

DOEpatents

Deason, Vance A.

1991-01-01

An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

Multiple acousto-optic q-switch

DOEpatents

Deason, Vance A.

1993-01-01

An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

Multiple acousto-optic q-switch

DOEpatents

Deason, Vance A.

1993-12-07

An improved dynamic moire interferometer comprised of a lasing medium providing a plurality of beams of coherent light, a multiple q-switch producing multiple trains of 100,000 or more pulses per second, a combining means collimating multiple trains of pulses into substantially a single train and directing beams to specimen gratings affixed to a test material, and a controller, triggering and sequencing the emission of the pulses with the occurrence and recording of a dynamic loading event.

Simulation of the excitation of quasi-plane wake waves in a plasma by a resonant sequence of laser pulses with a variable envelope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalinnikova, E. I.; Levchenko, V. D.

2008-04-15

Results are presented from full-scale numerical simulations of the excitation of wake waves by a sequence of weakly relativistic laser pulses in a subcritical plasma. Computations were carried out with a 2D3V version of the SUR-CA code that is based on the local-recursive nonlocal-asynchronous algorithm of the particle-in-cell method. The parameters of a train of laser pulses were chosen to correspond to the resonant excitation of the wake field. The curvature of the envelope of the pulses was chosen to depend on the number of the pulse in the train. Numerical simulations showed that there are plane waves during themore » first period of the plasma wave behind the pulse train.« less

Generation of bright attosecond x-ray pulse trains via Thomson scattering from laser-plasma accelerators.

PubMed

Luo, W; Yu, T P; Chen, M; Song, Y M; Zhu, Z C; Ma, Y Y; Zhuo, H B

2014-12-29

Generation of attosecond x-ray pulse attracts more and more attention within the advanced light source user community due to its potentially wide applications. Here we propose an all-optical scheme to generate bright, attosecond hard x-ray pulse trains by Thomson backscattering of similarly structured electron beams produced in a vacuum channel by a tightly focused laser pulse. Design parameters for a proof-of-concept experiment are presented and demonstrated by using a particle-in-cell code and a four-dimensional laser-Compton scattering simulation code to model both the laser-based electron acceleration and Thomson scattering processes. Trains of 200 attosecond duration hard x-ray pulses holding stable longitudinal spacing with photon energies approaching 50 keV and maximum achievable peak brightness up to 10²⁰ photons/s/mm²/mrad²/0.1%BW for each micro-bunch are observed. The suggested physical scheme for attosecond x-ray pulse trains generation may directly access the fastest time scales relevant to electron dynamics in atoms, molecules and materials.

Evaluation of Material Nonlinearities Using Rectangular Pulse Trains for Excitation

NASA Astrophysics Data System (ADS)

Chaziachmetovas, Andrius; Svilainis, Linas; Kybartas, Darius; Aleksandrovas, Arturas; Liaukonis, Dobilas

Aim of the presented investigation was to evaluate the suitability of the rectangular pulse trains for nonlinear material parameters study. It was assumed that if duty cycle of the excitation is 50% then second harmonic is significantly reduced. Excitation signal frequency was fixed to the A/D sampling frequency and signal carefully gated to reduce the signal leak into neighbouring frequency bins. Sine wave correlation was used to extract the harmonics content. Results of nonlinear parameters measurement for several materials are given as performance comparison.

Method and apparatus for measuring frequency and phase difference

NASA Technical Reports Server (NTRS)

Shores, Paul (Inventor); Lichtenberg, Christopher (Inventor); Kobayashi, Herbert S. (Inventor); Cunningham, Allen R. (Inventor)

1986-01-01

The present invention is a system for deriving direct digital indications of frequency and phase difference between two incoming pulse trains adaptable for collision avoidance systems or the like. A pair of radar beams are directed toward a target and corresponding beams returning therefrom are detected. A digital difference circuit forms a pulse train from the Doppler shift frequencies of each beam pair having a repetition rate functionally related to the difference in magnitude of the shift frequencies. Pulses from the pulse train are counted as a function of time. Visual indications thereof on display are correlative to target position relative to beams.

Low frequency, ca. 40 Hz, pulse trains recorded in the humpback whale assembly in Hawaii.

PubMed

Darling, James D

2015-11-01

During studies of humpback whale song and social sounds in Hawaii, bouts of low frequency (ca. 40 Hz) pulses were periodically recorded. One example was made near an active group of eight adults (included 22 bouts, 2-13 s long, over 90 min); another close to an adult male-female pair (12 bouts, 9-93 s long, over 22 min). The mean peak and center frequencies (39 to 40 Hz) and bandwidth (13 Hz) were similar in both, but the organization of the pulses differed. Song components, social sounds, bubble trains, or other species do not provide a ready explanation for this sound.

Beyond the single-atom response in absorption line shapes: probing a dense, laser-dressed helium gas with attosecond pulse trains.

PubMed

Liao, Chen-Ting; Sandhu, Arvinder; Camp, Seth; Schafer, Kenneth J; Gaarde, Mette B

2015-04-10

We investigate the absorption line shapes of laser-dressed atoms beyond the single-atom response, by using extreme ultraviolet (XUV) attosecond pulse trains to probe an optically thick helium target under the influence of a strong infrared (IR) field. We study the interplay between the IR-induced phase shift of the microscopic time-dependent dipole moment and the resonant-propagation-induced reshaping of the macroscopic XUV pulse. Our experimental and theoretical results show that as the optical depth increases, this interplay leads initially to a broadening of the IR-modified line shape, and subsequently, to the appearance of new, narrow features in the absorption line.

Effects of cochlear-implant pulse rate and inter-channel timing on channel interactions and thresholds

NASA Astrophysics Data System (ADS)

Middlebrooks, John C.

2004-07-01

Interactions among the multiple channels of a cochlear prosthesis limit the number of channels of information that can be transmitted to the brain. This study explored the influence on channel interactions of electrical pulse rates and temporal offsets between channels. Anesthetized guinea pigs were implanted with 2-channel scala-tympani electrode arrays, and spike activity was recorded from the auditory cortex. Channel interactions were quantified as the reduction of the threshold for pulse-train stimulation of the apical channel by sub-threshold stimulation of the basal channel. Pulse rates were 254 or 4069 pulses per second (pps) per channel. Maximum threshold reductions averaged 9.6 dB when channels were stimulated simultaneously. Among nonsimultaneous conditions, threshold reductions at the 254-pps rate were entirely eliminated by a 1966-μs inter-channel offset. When offsets were only 41 to 123 μs, however, maximum threshold shifts averaged 3.1 dB, which was comparable to the dynamic ranges of cortical neurons in this experimental preparation. Threshold reductions at 4069 pps averaged up to 1.3 dB greater than at 254 pps, which raises some concern in regard to high-pulse-rate speech processors. Thresholds for various paired-pulse stimuli, pulse rates, and pulse-train durations were measured to test possible mechanisms of temporal integration.

Dual comb generation from a mode-locked fiber laser with orthogonally polarized interlaced pulses.

PubMed

Akosman, Ahmet E; Sander, Michelle Y

2017-08-07

Ultra-high precision dual-comb spectroscopy traditionally requires two mode-locked, fully stabilized lasers with complex feedback electronics. We present a novel mode-locked operation regime in a thulium-holmium co-doped fiber laser, a frequency-halved state with orthogonally polarized interlaced pulses, for dual comb generation from a single source. In a linear fiber laser cavity, an ultrafast pulse train composed of co-generated, equal intensity and orthogonally polarized consecutive pulses at half of the fundamental repetition rate is demonstrated based on vector solitons. Upon optical interference of the orthogonally polarized pulse trains, two stable microwave RF beat combs are formed, effectively down-converting the optical properties into the microwave regime. These co-generated, dual polarization interlaced pulse trains, from one all-fiber laser configuration with common mode suppression, thus provide an attractive compact source for dual-comb spectroscopy, optical metrology and polarization entanglement measurements.

Control of wavepacket dynamics in mixed alkali metal clusters by optimally shaped fs pulses

NASA Astrophysics Data System (ADS)

Bartelt, A.; Minemoto, S.; Lupulescu, C.; Vajda, Š.; Wöste, L.

We have performed adaptive feedback optimization of phase-shaped femtosecond laser pulses to control the wavepacket dynamics of small mixed alkali-metal clusters. An optimization algorithm based on Evolutionary Strategies was used to maximize the ion intensities. The optimized pulses for NaK and Na2K converged to pulse trains consisting of numerous peaks. The timing of the elements of the pulse trains corresponds to integer and half integer numbers of the vibrational periods of the molecules, reflecting the wavepacket dynamics in their excited states.

Digital coincidence counting

NASA Astrophysics Data System (ADS)

Buckman, S. M.; Ius, D.

1996-02-01

This paper reports on the development of a digital coincidence-counting system which comprises a custom-built data acquisition card and associated PC software. The system has been designed to digitise the pulse-trains from two radiation detectors at a rate of 20 MSamples/s with 12-bit resolution. Through hardware compression of the data, the system can continuously record both individual pulse-shapes and the time intervals between pulses. Software-based circuits are used to process the stored pulse trains. These circuits are constructed simply by linking together icons representing various components such as coincidence mixers, time delays, single-channel analysers, deadtimes and scalers. This system enables a pair of pulse trains to be processed repeatedly using any number of different methods. Some preliminary results are presented in order to demonstrate the versatility and efficiency of this new method.

In vivo lactate and beta-hydroxybutyrate editing using a pure-phase refocusing pulse train.

PubMed

Shen, J; Novotny, E J; Rothman, D L

1998-11-01

A refocusing pulse train consisting of a semiselective refocusing pulse and a selective inversion pulse to obtain a pure-phase refocusing at the frequency of maximal excitation of the semiselective refocusing pulse is proposed and applied to in vivo lactate and beta-hydroxybutyrate editing using difference spectroscopy. It is shown, using both rotation matrix theory and phantom experiments, that the soft inversion pulse has to be halved to flank the semiselective pulse to obtain perfect refocusing and cancellation of interfering resonances. The editing method is used to obtain lactate and beta-hydroxybutyrate spectra from the occipital cortex of juvenile epilepsy patients before and after ketogenic diet treatment.

Temperature dependence of the pulse-duration memory effect in NbSe3

NASA Astrophysics Data System (ADS)

Jones, T. C.; Simpson, C. R., Jr.; Clayhold, J. A.; McCarten, J. P.

2000-04-01

The temperature dependence of the oscillatory response of the 59 K charge-density wave in NbSe3 to a sequence of repetitive current pulses was investigated. For 52 K>T>45 K the learned behavior commonly referred to as the pulse-duration memory effect (PDME) is very evident; after training the voltage oscillation always finishes the pulse at a minimum. At lower temperatures the PDME changes qualitatively. In nonswitching samples the voltage oscillation always finishes the pulse increasing. In switching samples there is a conduction delay which becomes fixed after training, but no learning of the duration of the pulse.

Properties of the unusually short pulse sequences occurring prior to the first strokes of negative cloud-to-ground lightning flashes

NASA Astrophysics Data System (ADS)

Kolmasova, Ivana; Santolik, Ondrej; Farges, Thomas; Rison, William; Lan, Radek; Uhlir, Ludek

2014-05-01

We analyze pulse sequences occurring prior to first return strokes of negative cloud-to-ground lightning flashes. The magnetic-field waveforms are measured close to the thunderstorm using a broad-band analyzer with a sampling interval of 12.5 ns. The electric-field waveforms are measured at the distance of ~ 400 km using an analyzer with a sampling interval of 80 ns. The sequence is usually composed of three parts. It begins with a larger pulse train which is believed to be connected with initial breakdown processes. The train of preliminary breakdown pulses ("B" part) is followed by a relatively low and irregular pulse activity ("I" part), which is sometimes missing. The sequence ends with a pulse train attributed to the stepped leader ("L" part). We recognize two different patterns ("B-I-L" and "B-L" types) in recorded waveforms. For the first time, we analyze the time evolution of the pulse amplitudes in the "B" part of "B-I-L" type sequences. The pulse amplitude is decreasing on average by 34% of the maximum value within a given train. We observe an unusually short duration of sequences. This is probably linked to a low height of the thundercloud. Another possible explanation may be based on an untypical precipitation mix resulting in faster steeped leaders.

X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging.

PubMed

Koerner, Lucas J; Gruner, Sol M

2011-03-01

Dynamic X-ray studies can reach temporal resolutions limited by only the X-ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in-pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count-rate limitations and in-pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high-speed laser measurements are shown. The detector resolved individual bunch trains at the Cornell High Energy Synchrotron Source at levels of up to 3.7 × 10(3) X-rays per pixel per train. When applied to turn-by-turn X-ray beam characterization, single-shot intensity measurements were made with a repeatability of 0.4% and horizontal oscillations of the positron cloud were detected.

X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging

PubMed Central

Koerner, Lucas J.; Gruner, Sol M.

2011-01-01

Dynamic X-ray studies can reach temporal resolutions limited by only the X-ray pulse duration if the detector is fast enough to segregate synchrotron pulses. An analog integrating pixel array detector with in-pixel storage and temporal resolution of around 150 ns, sufficient to isolate pulses, is presented. Analog integration minimizes count-rate limitations and in-pixel storage captures successive pulses. Fundamental tests of noise and linearity as well as high-speed laser measurements are shown. The detector resolved individual bunch trains at the Cornell High Energy Synchrotron Source at levels of up to 3.7 × 103 X-rays per pixel per train. When applied to turn-by-turn X-ray beam characterization, single-shot intensity measurements were made with a repeatability of 0.4% and horizontal oscillations of the positron cloud were detected. PMID:21335901

Active/passive mode-locked laser oscillator

DOEpatents

Fountain, William D.; Johnson, Bertram C.

1977-01-01

A Q-switched/mode-locked Nd:YAG laser oscillator employing simultaneous active (electro-optic) and passive (saturable absorber) loss modulation within the optical cavity is described. This "dual modulation" oscillator can produce transform-limited pulses of duration ranging from about 30 psec to about 5 nsec with greatly improved stability compared to other mode-locked systems. The pulses produced by this system lack intrapulse frequency or amplitude modulation, and hence are idealy suited for amplification to high energies and for other applications where well-defined pulses are required. Also, the pulses of this system have excellent interpulse characteristics, wherein the optical noise between the individual pulses of the pulse train has a power level well below the power of the peak pulse of the train.

Interactions between rewarding lateral hypothalamic and aversive nucleus reticularis gigantocellularis stimulation.

PubMed

Diotte, M; Miguelez, M; Miliaressis, E; Bielajew, C

2000-12-05

The interaction between rewarding and aversive consequences of brain stimulation were assessed in two studies. In the first, the frequency threshold for 300 ms trains of combined lateral hypothalamic (LH) and nucleus reticularis gigantocellularis (Gi) stimulation, in which each LH pulse was followed 2 ms later by the Gi one, was determined for one month. Compared to the threshold for trains of single LH pulses, combined LH-Gi stimulation initially increased the frequency threshold; however, this effect reversed within one session and was subsequently maintained for the duration of the study. The aversion produced by Gi stimulation, as measured by latency to escape, was abolished following a single session of LH-Gi pairs. In the second study, a subset of animals received both presentations of combined pulses, LH followed by Gi, and the reverse; the interval between pulses was varied from 0.2 to 6.4 ms. The effectiveness of combined stimulation, determined by the ratio of LH frequency thresholds to that of the LH-Gi ranged from 0 to 50% across animals but the individual effectiveness functions within animals did not vary with different intervals. In addition, the order of presentation of pulses was of no consequence. Thus, not only did exposure to LH stimulation appear to obliterate Gi aversion, but the combination of LH and Gi pulses added to the rewarding effect produced by LH stimulation alone.

Detailed characteristics of intermittent current pulses due to positive corona

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yang, E-mail: liuyangwuh520@sina.com; Cui, Xiang; Lu, Tiebing

In order to get detailed characteristics of intermittent current pulses due to positive corona such as the repetition rate of burst-pulse trains, the peak value ratio of the primary pulse to the secondary pulse, the number of pulses per burst, and the interval of the secondary pulses, a systematic study was carried out in a coaxial conductor-cylinder electrode system with the conductor electrode being set with a discharge point. Empirical formulae for the number of pulses per burst and the interval of the secondary pulses are first presented. A theoretical model based on the motion of the space-charge clouds ismore » proposed. Analysis with the model gives explanations to the experimental results and reveals some new insights into the physical mechanism of positive intermittent corona.« less

Changes in auditory nerve responses across the duration of sinusoidally amplitude-modulated electric pulse-train stimuli.

PubMed

Hu, Ning; Miller, Charles A; Abbas, Paul J; Robinson, Barbara K; Woo, Jihwan

2010-12-01

Response rates of auditory nerve fibers (ANFs) to electric pulse trains change over time, reflecting substantial spike-rate adaptation that depends on stimulus parameters. We hypothesize that adaptation affects the representation of amplitude-modulated pulse trains used by cochlear prostheses to transmit speech information to the auditory system. We recorded cat ANF responses to sinusoidally amplitude-modulated (SAM) trains with 5,000 pulse/s carriers. Stimuli delivered by a monopolar intracochlear electrode had fixed modulation frequency (100 Hz) and depth (10%). ANF responses were assessed by spike-rate measures, while representation of modulation was evaluated by vector strength (VS) and the fundamental component of the fast Fourier transform (F(0) amplitude). These measures were assessed across the 400 ms duration of pulse-train stimuli, a duration relevant to speech stimuli. Different stimulus levels were explored and responses were categorized into four spike-rate groups to assess level effects across ANFs. The temporal pattern of rate adaptation to modulated trains was similar to that of unmodulated trains, but with less rate adaptation. VS to the modulator increased over time and tended to saturate at lower spike rates, while F(0) amplitude typically decreased over time for low driven rates and increased for higher driven rates. VS at moderate and high spike rates and degree of F(0) amplitude temporal changes at low and moderate spike rates were positively correlated with the degree of rate adaptation. Thus, high-rate carriers will modify the ANF representation of the modulator over time. As the VS and F(0) measures were sensitive to adaptation-related changes over different spike-rate ranges, there is value in assessing both measures.

Taking the Pulse of Training Transfer: Instructor Quality and EMT Certification Examination Results

ERIC Educational Resources Information Center

Russ-Eft, Darlene F.; Dickison, Phil; Levine, Roger

2010-01-01

The Longitudinal Emergency Medical Technician Attributes and Demographics Study (LEADS) provides a representative sampling of EMTs throughout the United States. The present study adds to the transfer of training literature by examining the relationship between instructor quality and National Registry of Emergency Medical Technicians certification…

The neuronal response to electrical constant-amplitude pulse train stimulation: additive Gaussian noise.

PubMed

Matsuoka, A J; Abbas, P J; Rubinstein, J T; Miller, C A

2000-11-01

Experimental results from humans and animals show that electrically evoked compound action potential (EAP) responses to constant-amplitude pulse train stimulation can demonstrate an alternating pattern, due to the combined effects of highly synchronized responses to electrical stimulation and refractory effects (Wilson et al., 1994). One way to improve signal representation is to reduce the level of across-fiber synchrony and hence, the level of the amplitude alternation. To accomplish this goal, we have examined EAP responses in the presence of Gaussian noise added to the pulse train stimulus. Addition of Gaussian noise at a level approximately -30 dB relative to EAP threshold to the pulse trains decreased the amount of alternation, indicating that stochastic resonance may be induced in the auditory nerve. The use of some type of conditioning stimulus such as Gaussian noise may provide a more 'normal' neural response pattern.

High resolution data acquisition

DOEpatents

Thornton, G.W.; Fuller, K.R.

1993-04-06

A high resolution event interval timing system measures short time intervals such as occur in high energy physics or laser ranging. Timing is provided from a clock, pulse train, and analog circuitry for generating a triangular wave synchronously with the pulse train (as seen in diagram on patent). The triangular wave has an amplitude and slope functionally related to the time elapsed during each clock pulse in the train. A converter forms a first digital value of the amplitude and slope of the triangle wave at the start of the event interval and a second digital value of the amplitude and slope of the triangle wave at the end of the event interval. A counter counts the clock pulse train during the interval to form a gross event interval time. A computer then combines the gross event interval time and the first and second digital values to output a high resolution value for the event interval.

High resolution data acquisition

DOEpatents

Thornton, Glenn W.; Fuller, Kenneth R.

1993-01-01

A high resolution event interval timing system measures short time intervals such as occur in high energy physics or laser ranging. Timing is provided from a clock (38) pulse train (37) and analog circuitry (44) for generating a triangular wave (46) synchronously with the pulse train (37). The triangular wave (46) has an amplitude and slope functionally related to the time elapsed during each clock pulse in the train. A converter (18, 32) forms a first digital value of the amplitude and slope of the triangle wave at the start of the event interval and a second digital value of the amplitude and slope of the triangle wave at the end of the event interval. A counter (26) counts the clock pulse train (37) during the interval to form a gross event interval time. A computer (52) then combines the gross event interval time and the first and second digital values to output a high resolution value for the event interval.

High power solid state laser modulator

DOEpatents

Birx, Daniel L.; Ball, Don G.; Cook, Edward G.

2004-04-27

A multi-stage magnetic modulator provides a pulse train of .+-.40 kV electrical pulses at a 5-7 kHz repetition rate to a metal vapor laser. A fractional turn transformer steps up the voltage by a factor of 80 to 1 and magnetic pulse compression is used to reduce the pulse width of the pulse train. The transformer is fabricated utilizing a rod and plate stack type of construction to achieve a high packing factor. The pulses are controlled by an SCR stack where a plurality of SCRs are electrically connected in parallel, each SCR electrically connected to a saturable inductor, all saturable inductors being wound on the same core of magnetic material for enhanced power handling characteristics.

Interferometric correction system for a numerically controlled machine

DOEpatents

Burleson, Robert R.

1978-01-01

An interferometric correction system for a numerically controlled machine is provided to improve the positioning accuracy of a machine tool, for example, for a high-precision numerically controlled machine. A laser interferometer feedback system is used to monitor the positioning of the machine tool which is being moved by command pulses to a positioning system to position the tool. The correction system compares the commanded position as indicated by a command pulse train applied to the positioning system with the actual position of the tool as monitored by the laser interferometer. If the tool position lags the commanded position by a preselected error, additional pulses are added to the pulse train applied to the positioning system to advance the tool closer to the commanded position, thereby reducing the lag error. If the actual tool position is leading in comparison to the commanded position, pulses are deleted from the pulse train where the advance error exceeds the preselected error magnitude to correct the position error of the tool relative to the commanded position.

Multi-operational tuneable Q-switched mode-locking Er fibre laser

NASA Astrophysics Data System (ADS)

Qamar, F. Z.

2018-01-01

A wavelength-spacing tuneable, Q-switched mode-locking (QML) erbium-doped fibre laser based on non-linear polarization rotation controlled by four waveplates and a cube polarizer is proposed. A mode-locked pulse train using two quarter-wave plates and a half-wave plate (HWP) is obtained first, and then an extra HWP is inserted into the cavity to produce different operation regimes. The evolutions of temporal and spectral dynamics with different orientation angles of the extra HWP are investigated. A fully modulated stable QML pulse train is observed experimentally. This is, to the author’s best knowledge, the first experimental work reporting QML operation without adding an extra saturable absorber inside the laser cavity. Multi-wavelength pulse laser operation, multi-pulse train continuous-wave mode-locking operation and pulse-splitting operations are also reported at certain HWP angles. The observed operational dynamics are interpreted as a mutual interaction of dispersion, non-linear effect and insertion loss. This work provides a new mechanism for fabricating cheap tuneable multi-wavelength lasers with QML pulses.

A train of electrical pulses applied to the primary auditory cortex evokes a conditioned response in guinea pigs.

PubMed

Okuda, Yuji; Shikata, Hiroshi; Song, Wen-Jie

2011-09-01

As a step to develop auditory prosthesis by cortical stimulation, we tested whether a single train of pulses applied to the primary auditory cortex could elicit classically conditioned behavior in guinea pigs. Animals were trained using a tone as the conditioned stimulus and an electrical shock to the right eyelid as the unconditioned stimulus. After conditioning, a train of 11 pulses applied to the left AI induced the conditioned eye-blink response. Cortical stimulation induced no response after extinction. Our results support the feasibility of auditory prosthesis by electrical stimulation of the cortex. Copyright © 2011 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

Sound spectrum of a pulsating optical discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grachev, G N; Smirnov, A L; Tishchenko, V N

A spectrum of sound of an optical discharge generated by a repetitively pulsed (RP) laser radiation has been investigated. The parameters of laser radiation are determined at which the spectrum of sound may contains either many lines, or the main line at the pulse repetition rate and several weaker overtones, or a single line. The spectrum of sound produced by trains of RP radiation comprises the line (and overtones) at the repetition rate of train sequences and the line at the repetition rate of pulses in trains. A CO{sub 2} laser with the pulse repetition rate of f ≈ 3more » – 180 kHz and the average power of up to 2 W was used in the experiments. (optical discharges)« less

Effect of second harmonic in pulse-width-modulation-based DAC for feedback of digital fluxgate magnetometer

NASA Astrophysics Data System (ADS)

Belyayev, Serhiy; Ivchenko, Nickolay

2018-04-01

Digital fluxgate magnetometers employ processing of the measured pickup signal to produce the value of the compensation current. Using pulse-width modulation with filtering for digital to analog conversion is a convenient approach, but it can introduce an intrinsic source of nonlinearity, which we discuss in this design note. A code shift of one least significant bit changes the second harmonic content of the pulse train, which feeds into the pick-up signal chain despite the heavy filtering. This effect produces a code-dependent nonlinearity. This nonlinearity can be overcome by the specific design of the timing of the pulse train signal. The second harmonic is suppressed if the first and third quarters of the excitation period pulse train are repeated in the second and fourth quarters. We demonstrate this principle on a digital magnetometer, achieving a magnetometer noise level corresponding to that of the sensor itself.

Biofeedback-assisted relaxation training to decrease test anxiety in nursing students.

PubMed

Prato, Catherine A; Yucha, Carolyn B

2013-01-01

Nursing students experiencing debilitating test anxiety may be unable to demonstrate their knowledge and have potential for poor academic performance. A biofeedback-assisted relaxation training program was created to reduce test anxiety. Anxiety was measured using Spielberger's Test Anxiety Inventory and monitoring peripheral skin temperature, pulse, and respiration rates during the training. Participants were introduced to diaphragmatic breathing, progressive muscle relaxation, and autogenic training. Statistically significant changes occurred in respiratory rates and skin temperatures during the diaphragmatic breathing session; respiratory rates and peripheral skin temperatures during progressive muscle relaxation session; respiratory and pulse rates, and peripheral skin temperatures during the autogenic sessions. No statistically significant difference was noted between the first and second TAI. Subjective test anxiety scores of the students did not decrease by the end of training. Autogenic training session was most effective in showing a statistically significant change in decreased respiratory and pulse rates and increased peripheral skin temperature.

Electrical stimulation of microengineered skeletal muscle tissue: Effect of stimulus parameters on myotube contractility and maturation.

PubMed

Banan Sadeghian, Ramin; Ebrahimi, Majid; Salehi, Sahar

2018-04-01

Skeletal muscle tissues engineered in vitro are aneural, are short in the number of fibres required to function properly and degenerate rapidly. Electrical stimulation has been widely used to compensate for such a lack of neural activity, yet the relationship between the stimulation parameters and the tissue response is subject to debate. Here we studied the effect of overnight electrical stimulation (training) on the contractility and maturity of aligned C2C12 myotubes developed on micropatterned gelatin methacryloyl (GelMA) substrates. Bipolar rectangular pulse (BRP) trains with frequency, half-duration and applied pulse train amplitudes of f = 1 Hz, t on  = 0.5 ms and V app  = {3 V, 4 V, 4.5 V}, respectively, were applied for 12 h to the myotubes formed on the microgrooved substrates. Aligned myotubes were contracting throughout the training period for V app  ≥ 4 V. Immediately after training, the samples were subjected to series of BRPs with 2 ≤ V app  ≤ 5 V and 0.2 ≤ t on  ≤ 0.9 ms, during which myotube contraction dynamics were recorded. Analysis of post-training contraction revealed that only the myotubes trained at V app  = 4 V displayed consistent and repeatable contraction profiles, showing the dynamics of myotube contractility as a function of triggering pulse voltage and current amplitudes, duration and imposed electrical energy. In addition, myotubes trained at V app  = 4 V displayed amplified expression levels of genes pertinent to sarcomere development correlated with myotube maturation. Our findings are imperative for a better understanding of the influence of electrical pulses on the maturation of microengineered myotubes. Copyright © 2017 John Wiley & Sons, Ltd.

Theoretical and Experimental Investigations of Coincidences in Poisson Distributed Pulse Trains and Spectral Distortion Caused by Pulse Pileup.

NASA Astrophysics Data System (ADS)

Bristow, Quentin

1990-01-01

Part one of this two-part study is concerned with the multiple coincidences in pulse trains from X-ray and gamma radiation detectors which are the cause of pulse pileup. A sequence of pulses with inter-arrival times less than tau, the resolving time of the pulse-height analysis system used to acquire spectra, is called a multiple pulse string. Such strings can be classified on the basis of the number of pulses they contain, or the number of resolving times they cover. The occurrence rates of such strings are derived from theoretical considerations. Logic circuits were devised to make experimental measurements of multiple pulse string occurrence rates in the output from a NaI(Tl) scintillation detector over a wide range of count rates. Markov process theory was used to predict state transition rates in the logic circuits, enabling the experimental data to be checked rigorously for conformity with those predicted for a Poisson distribution. No fundamental discrepancies were observed. Part two of the study is concerned with a theoretical analysis of pulse pileup and the development of a discrete correction algorithm, based on the use of a function to simulate the coincidence spectrum produced by partial sums of pulses. Monte Carlo simulations, incorporating criteria for pulse pileup inherent in the operation of modern ADC's, were used to generate pileup spectra due to coincidences between two pulses, (1st order pileup) and three pulses (2nd order pileup), for different semi-Gaussian pulse shapes. Coincidences between pulses in a single channel produced a basic probability density function spectrum which can be regarded as an impulse response for a particular pulse shape. The use of a flat spectrum (identical count rates in all channels) in the simulations, and in a parallel theoretical analysis, showed the 1st order pileup distorted the spectrum to a linear ramp with a pileup tail. The correction algorithm was successfully applied to correct entire spectra for 1st and 2nd order pileup; both those generated by Monte Carlo simulations and in addition some real spectra acquired with a laboratory multichannel analysis system.

Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

NASA Astrophysics Data System (ADS)

Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

2013-09-01

A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

Dynamic optical arbitrary waveform generation with amplitude controlled by interference of two FBG arrays.

PubMed

Zhang, Ailing; Li, Changxiu

2012-10-08

In this paper, a novel structure of dynamic optical arbitrary waveform generation (O-AWG) with amplitude controlled by interference of two fiber Bragg grating (FBG) arrays is proposed. The FBG array consists of several FBGs and fiber stretchers (FSs). The amplitude is controlled by FSs through interference of two FBG arrays. The phase is controlled by FSs simultaneously. As a result, optical pulse trains with various waveforms as well as pulse trains with nonuniform pulse intensity, pulse spacing and pulse width in each period are obtained via FSs adjustment to change the phase shift of signal in each array.

Architecture and Bloch-Maxwell modelling of multi-mJ 100 fs fully-coherent soft X-ray laser based on X-ray CPA

NASA Astrophysics Data System (ADS)

Zeitoun, Ph.; Oliva, E.; Fajardo, M.; Cheriaux, G.; Le, T. T. T.; Li, L.; Pitman, M.; Ros, D.; Sebban, S.; Velarde, P.

2012-07-01

By seeding amplifying plasmas pumped with the so-called Transient collisionnal excitation scheme, the amplified pulse seems to be limited to an energy of several 10's of μJ. Aiming to attain several mJ, we study the seeding of plasma pumped by long laser pulse. Thanks to our time-dependent Maxwell-Bloch code, we demonstrate that direct seeding with femtosecond pulse is inefficient. We also study the amplification of pulse train with the drawback of re-synchronizing the pulses. We proposed and studied the amplification of high harmonic seed stretched by a grating pair, amplified finally compressed. We consider off-axis diffraction on the gratings for maximizing their efficiency. Considering the phase deformation induced by the amplification and the spectral narrowing the final pulse is 230 fs in duration and 5 mJ.

Architecture and Bloch-Maxwell modelling of multi-mJ 100 fs fully-coherent soft X-ray laser based on X-ray CPA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeitoun, Ph.; Oliva, E.; Fajardo, M.

2012-07-09

By seeding amplifying plasmas pumped with the so-called Transient collisionnal excitation scheme, the amplified pulse seems to be limited to an energy of several 10's of {mu}J. Aiming to attain several mJ, we study the seeding of plasma pumped by long laser pulse. Thanks to our time-dependent Maxwell-Bloch code, we demonstrate that direct seeding with femtosecond pulse is inefficient. We also study the amplification of pulse train with the drawback of re-synchronizing the pulses. We proposed and studied the amplification of high harmonic seed stretched by a grating pair, amplified finally compressed. We consider off-axis diffraction on the gratings formore » maximizing their efficiency. Considering the phase deformation induced by the amplification and the spectral narrowing the final pulse is 230 fs in duration and 5 mJ.« less

Impact of Short-Term Training Camp on Aortic Blood Pressure in Collegiate Endurance Runners

PubMed Central

Tomoto, Tsubasa; Sugawara, Jun; Hirasawa, Ai; Imai, Tomoko; Maeda, Seiji; Ogoh, Shigehiko

2018-01-01

To investigate the influence of short-term vigorous endurance training on aortic blood pressure (BP), pulse wave analysis was performed in 36 highly trained elite collegiate endurance runners before and after a 7-day intense training camp. Subjects participated three training sessions per day, which mainly consisted of long distance running and sprint training to reach the daily target distance of 26 km. After the camp, they were divided into two groups based on whether the target training was achieved. Aortic systolic BP, pulse pressure, and tension-time index (TTI, a surrogate index of the myocardial oxygen demand) were significantly elevated after the camp in the accomplished group but not in the unaccomplished group, whereas the brachial BP remained unchanged in both groups. The average daily training distance was significantly correlated with the changes in aortic systolic BP (r = 0.608, p = 0.0002), pulse pressure (r = 0.415, p = 0.016), and TTI (r = 0.438, p = 0.011). These results suggest that aortic BP is affected by a short-term vigorous training camp even in highly trained elite endurance athletes presumably due to a greater training volume compared to usual. PMID:29643814

Aerobic or Resistance Training and Pulse Wave Velocity in Kidney Transplant Recipients: A 12-Week Pilot Randomized Controlled Trial (the Exercise in Renal Transplant [ExeRT] Trial).

PubMed

Greenwood, Sharlene A; Koufaki, Pelagia; Mercer, Thomas H; Rush, Robert; O'Connor, Ellen; Tuffnell, Rachel; Lindup, Herolin; Haggis, Lynda; Dew, Tracy; Abdulnassir, Lyndsey; Nugent, Eilish; Goldsmith, David; Macdougall, Iain C

2015-10-01

Cardiovascular disease remains the leading cause of death in kidney transplant recipients. This pilot study examined the potential effect of aerobic training or resistance training on vascular health and indexes of cardiovascular risk in kidney transplant recipients. Single-blind, randomized, controlled, parallel trial. 60 participants (mean age, 54 years; 34 men) were randomly assigned to aerobic training (n=20), resistance training (n=20), or usual care (n=20). Participants were included if they had a kidney transplant within 12 months prior to baseline assessment. Patients were excluded if they had unstable medical conditions or had recently started regular exercise. Aerobic training and resistance training were delivered 3 days per week for a 12-week period. The usual-care group received standard care. Pulse wave velocity, peak oxygen uptake (Vo2peak), sit-to-stand 60, isometric quadriceps force, and inflammatory biomarkers were assessed at 0 and 12 weeks. The anticipated 60 participants were recruited within 12 months. 46 participants completed the study (aerobic training, n=13; resistance training, n=13; and usual care, n=20), resulting in a 23% attrition rate. Analyses of covariance, adjusted for baseline values, age, and dialysis vintage pretransplantation, revealed significant mean differences between aerobic training and usual care in pulse wave velocity of -2.2±0.4 (95% CI, -3.1 to -1.3) m/s (P<0.001) and between resistance training and usual care of -2.6±0.4 (95% CI, -3.4 to -1.7) m/s (P<0.001) at 12 weeks. Secondary analyses indicated significant improvements in Vo2peak in the aerobic training group and in Vo2peak, sit-to-stand 60, and isometric muscle force in the resistance training group compared with usual care at 12 weeks. There were no reported adverse events, cardiovascular events, or hospitalizations as a result of the intervention. Pilot study, small sample size, no measure of endothelial function. Both aerobic training and resistance training interventions appear to be feasible and clinically beneficial in this patient population. Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Optimal timing of pulse onset for language mapping with navigated repetitive transcranial magnetic stimulation.

PubMed

Krieg, Sandro M; Tarapore, Phiroz E; Picht, Thomas; Tanigawa, Noriko; Houde, John; Sollmann, Nico; Meyer, Bernhard; Vajkoczy, Peter; Berger, Mitchel S; Ringel, Florian; Nagarajan, Srikantan

2014-10-15

Within the primary motor cortex, navigated transcranial magnetic stimulation (nTMS) has been shown to yield maps strongly correlated with those generated by direct cortical stimulation (DCS). However, the stimulation parameters for repetitive nTMS (rTMS)-based language mapping are still being refined. For this purpose, the present study compares two rTMS protocols, which differ in the timing of pulse train onset relative to picture presentation onset during object naming. Results were the correlated with DCS language mapping during awake surgery. Thirty-two patients with left-sided perisylvian tumors were examined by rTMS prior to awake surgery. Twenty patients underwent rTMS pulse trains starting at 300 ms after picture presentation onset (delayed TMS), whereas another 12 patients received rTMS pulse trains starting at the picture presentation onset (ONSET TMS). These rTMS results were then evaluated for correlation with intraoperative DCS results as gold standard in terms of differential consistencies in receiver operating characteristics (ROC) statistics. Logistic regression analysis by protocols and brain regions were conducted. Within and around Broca's area, there was no difference in sensitivity (onset TMS: 100%, delayed TMS: 100%), negative predictive value (NPV) (onset TMS: 100%, delayed TMS: 100%), and positive predictive value (PPV) (onset TMS: 55%, delayed TMS: 54%) between the two protocols compared to DCS. However, specificity differed significantly (onset TMS: 67%, delayed TMS: 28%). In contrast, for posterior language regions, such as supramarginal gyrus, angular gyrus, and posterior superior temporal gyrus, early pulse train onset stimulation showed greater specificity (onset TMS: 92%, delayed TMS: 20%), NPV (onset TMS: 92%, delayed TMS: 57%) and PPV (onset TMS: 75%, delayed TMS: 30%) with comparable sensitivity (onset TMS: 75%, delayed TMS: 70%). Logistic regression analysis also confirmed the greater fit of the predictions by rTMS that had the pulse train onset coincident with the picture presentation onset when compared to the delayed stimulation. Analyses of differential disruption patterns of mapped cortical regions were further able to distinguish clusters of cortical regions standardly associated with semantic and pre-vocalization phonological networks proposed in various models of word production. Repetitive nTMS predictions by both protocols correlate well with DCS outcomes especially in Broca's region, particularly with regard to TMS negative predictions. With this study, we have demonstrated that rTMS stimulation onset coincident with picture presentation onset improves the accuracy of preoperative language maps, particularly within posterior language areas. Moreover, immediate and delayed pulse train onsets may have complementary disruption patterns that could differentially capture cortical regions causally necessary for semantic and pre-vocalization phonological networks. Published by Elsevier Inc.

Evaluation of stimulation parameters on aortomyoplasty, using Latissimus Dorsi muscle in a goat model: an acute study.

PubMed

Hakami, A; Santamore, W P; Stremel, R W; Tobin, G; Hjortdal, V E

1999-08-01

Dynamic aortomyoplasty using Latissimus Dorsi muscle (LDM) has been shown to improve myocardial function. However, systematic examination of the effects of stimulation parameters on aortic wrap function has not been done. Thus, the present study measures the direct effect of stimulation voltage, pulse train duration, frequency of the pulses, and the duration of the stimulation delay from R wave on the aortic wrap function. In eight female goats, the left LDM was wrapped around the descending aorta. The muscle was then subjected to electrical stimulation, altering frequency of stimulation pulses (16.6, 20, 25, 33 and 50 Hz), amplitude (2, 4, 6, 8 and 10 V), and number of pulses (2, 4, 6, 8 and 10 pulses) in a train stimulation. Left ventricular, aortic pressure, and pressure generated by LDM on aorta (wrap pressure) was measured. The changes in hemodynamic parameters mentioned above were calculated and compared for different stimulation parameters during unassisted and assisted cardiac cycles. Aortomyoplasty counterpulsation using LDM provided significant improvement in wrap pressure (78 mmHg +/- 2), aortic diastolic pressure, and changes in aortic diastolic pressure from 2 to 4 V (P < 0.05). Further increase in amplitude did not make any significant improvements of the above mentioned parameters. Significant augmentation of wrap pressure (82 mmHg +/- 2), aortic diastolic pressure (79 mmHg +/- 3) and changes in aortic diastolic pressure (12 mmHg +/- 1) occurred at 6 pulses (P < 0.05). Other changes in number of pulses did not show any significant improvements. Significant improvement of wrap pressure (80 mmHg +/- 2), aortic diastolic pressure (73 mmHg +/- 3) and changes in aortic diastolic pressure (12 mmHg +/- 1) was observed with a frequency of 33 Hz. To examine a wide range of delays from the onset of the QRS complex to LDM stimulation, stimulation was delivered randomly. The exact delay was determined from the ECG signal and superimposed LDM stimulation pulses. In this study we present a new measurement, wrap pressure. We also present that in aortomyoplasty using LDM, the most significant improvement in wrap pressure, aortic diastolic pressure and changes in aortic diastolic pressure occurs when the stimulation consists of an amplitude of 4 V, a frequency of 33 Hz and a train stimulation of 6 pulses.

Home-based anthropometric, blood pressure and pulse measurements in young children by trained data collectors in the National Children's Study.

PubMed

Zimowski, Michele; Moye, Jack; Dugoni, Bernard; Heim Viox, Melissa; Cohen, Hildie; Winfrey, Krishna

2017-02-01

The current study assessed whether home-based data collection by trained data collectors can produce high-quality physical measurement data in young children. The study assessed the quality of intra-examiner measurements of blood pressure, pulse rate and anthropometric dimensions using intra-examiner reliability and intra-examiner technical error of measurement (TEM). Non-clinical, primarily private homes of National Children's Study participants in twenty-two study locations across the USA. Children in four age groups: 5-7 months (n 91), 11-16 months (n 393), 23-28 months (n 1410) and 35-40 months (n 800). Absolute TEM ranged in value from 0·09 to 16·21, varying widely by age group and measure, as expected. Relative TEM spanned from 0·27 to 13·71 across age groups and physical measures. Reliabilities for anthropometric measurements by age group and measure ranged from 0·46 to >0·99 with most exceeding 0·90, suggesting that the large majority of anthropometric measures can be collected in a home-based setting on young children by trained data collectors. Reliabilities for blood pressure and pulse rate measurements by age group ranged from 0·21 to 0·74, implying these are less reliably measured with young children when taken in the data collection context described here. Reliability estimates >0·95 for weight, length, height, and thigh, waist and head circumference, and >0·90 for triceps and subscapular skinfolds, indicate that these measures can be collected in the field by trained data collectors without compromising data quality. These estimates can be used for interim evaluations of data collector training and measurement protocols.

Heterosynaptic modulation of evoked synaptic potentials in layer II of the entorhinal cortex by activation of the parasubiculum

PubMed Central

Sparks, Daniel W.

2016-01-01

The superficial layers of the entorhinal cortex receive sensory and associational cortical inputs and provide the hippocampus with the majority of its cortical sensory input. The parasubiculum, which receives input from multiple hippocampal subfields, sends its single major output projection to layer II of the entorhinal cortex, suggesting that it may modulate processing of synaptic inputs to the entorhinal cortex. Indeed, stimulation of the parasubiculum can enhance entorhinal responses to synaptic input from the piriform cortex in vivo. Theta EEG activity contributes to spatial and mnemonic processes in this region, and the current study assessed how stimulation of the parasubiculum with either single pulses or short, five-pulse, theta-frequency trains may modulate synaptic responses in layer II entorhinal stellate neurons evoked by stimulation of layer I afferents in vitro. Parasubicular stimulation pulses or trains suppressed responses to layer I stimulation at intervals of 5 ms, and parasubicular stimulation trains facilitated layer I responses at a train-pulse interval of 25 ms. This suggests that firing of parasubicular neurons during theta activity may heterosynaptically enhance incoming sensory inputs to the entorhinal cortex. Bath application of the hyperpolarization-activated cation current (Ih) blocker ZD7288 enhanced the facilitation effect, suggesting that cholinergic inhibition of Ih may contribute. In addition, repetitive pairing of parasubicular trains and layer I stimulation induced a lasting depression of entorhinal responses to layer I stimulation. These findings provide evidence that theta activity in the parasubiculum may promote heterosynaptic modulation effects that may alter sensory processing in the entorhinal cortex. PMID:27146979

Potential of M-Wave Elicited by Double Pulse for Muscle Fatigue Evaluation in Intermittent Muscle Activation by Functional Electrical Stimulation for Motor Rehabilitation

PubMed Central

Miura, Naoto; Watanabe, Takashi

2016-01-01

Clinical studies on application of functional electrical stimulation (FES) to motor rehabilitation have been increasing. However, muscle fatigue appears early in the course of repetitive movement production training by FES. Although M-wave variables were suggested to be reliable indices of muscle fatigue in long lasting constant electrical stimulation under the isometric condition, the ability of M-wave needs more studies under intermittent stimulation condition, because the intervals between electrical stimulations help recovery of muscle activation level. In this paper, M-waves elicited by double pulses were examined in muscle fatigue evaluation during repetitive movements considering rehabilitation training with surface electrical stimulation. M-waves were measured under the two conditions of repetitive stimulation: knee extension force production under the isometric condition and the dynamic movement condition by knee joint angle control. Amplitude of M-wave elicited by the 2nd pulse of a double pulse decreased during muscle fatigue in both measurement conditions, while the change in M-waves elicited by single pulses in a stimulation burst was not relevant to muscle fatigue in repeated activation with stimulation interval of 1 s. Fatigue index obtained from M-waves elicited by 2nd pulses was suggested to provide good estimation of muscle fatigue during repetitive movements with FES. PMID:27110556

Coupling of Action-Perception Brain Networks during Musical Pulse Processing: Evidence from Region-of-Interest-Based Independent Component Analysis.

PubMed

Burunat, Iballa; Tsatsishvili, Valeri; Brattico, Elvira; Toiviainen, Petri

2017-01-01

Our sense of rhythm relies on orchestrated activity of several cerebral and cerebellar structures. Although functional connectivity studies have advanced our understanding of rhythm perception, this phenomenon has not been sufficiently studied as a function of musical training and beyond the General Linear Model (GLM) approach. Here, we studied pulse clarity processing during naturalistic music listening using a data-driven approach (independent component analysis; ICA). Participants' (18 musicians and 18 controls) functional magnetic resonance imaging (fMRI) responses were acquired while listening to music. A targeted region of interest (ROI) related to pulse clarity processing was defined, comprising auditory, somatomotor, basal ganglia, and cerebellar areas. The ICA decomposition was performed under different model orders, i.e., under a varying number of assumed independent sources, to avoid relying on prior model order assumptions. The components best predicted by a measure of the pulse clarity of the music, extracted computationally from the musical stimulus, were identified. Their corresponding spatial maps uncovered a network of auditory (perception) and motor (action) areas in an excitatory-inhibitory relationship at lower model orders, while mainly constrained to the auditory areas at higher model orders. Results revealed (a) a strengthened functional integration of action-perception networks associated with pulse clarity perception hidden from GLM analyses, and (b) group differences between musicians and non-musicians in pulse clarity processing, suggesting lifelong musical training as an important factor that may influence beat processing.

Structure of picosecond pulses of a Q-switched and mode-locked diode-pumped Nd:YAG laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donin, V I; Yakovin, D V; Gribanov, A V

2015-12-31

The pulse duration of a diode-pumped Nd:YAG laser, in which Q-switching with mode-locking (QML regime) is achieved using a spherical mirror and a travelling-wave acousto-optic modulator, is directly measured with a streak camera. It is found that the picosecond pulses can have a non-single-pulse structure, which is explained by excitation of several competing transverse modes in the Q-switching regime with a pulse repetition rate of 1 kHz. In the case of cw mode-locking (without Q-switching), a new (auto-QML) regime is observed, in which the pulse train repetition rate is determined by the frequency of the relaxation oscillations of the lasermore » field while the train contains single picosecond pulses. (control of laser radiation parameters)« less

Determination of pulse profile characteristics of multi spot retinal photocoagulation lasers.

PubMed

Clarkson, Douglas McG; Makhzoum, Osama; Blackburn, John

2015-10-01

A system is described for determination of discrete pulse train characteristics of multi spot laser delivery systems for retinal photocoagulation. While photodiodes provide an ideal detection mechanism, measurement artifacts can potentially be introduced by the spatial pattern of the delivered beam relative to a discrete photodiode element. This problem was overcome by use of an integrating sphere to produce a uniform light field at the site of the photodiode detector. A basic current driven photodiode detection circuit incorporating an operational amplifier was used to generate a signal captured by a commercially available USB interface device at a rate of 10 kHz. Studies were undertaken of a Topcon Pascal Streamline laser system with output at a wavelength of 577 nm (yellow). This laser features the proprietary feature of 'Endpoint Management' ™ where pulses can be delivered as 100% of set energy levels with visible reaction on the retina and also at a reduced energy level to create potentially non visible but clinically effective lesions. Using the pulse train measurement device it was identified that the 'Endpoint Management' ™ delivery mode of pulses of lower energy was achieved by reducing the pulse duration of pulses for non-visible effect pulses while maintaining consistent beam power levels within the delivered pulse profile. The effect of eye geometry in determining safety and effectiveness of multi spot laser delivery for retinal photocoagulation is discussed. Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.

Asymmetric noise sensitivity of pulse trains in an excitable microlaser with delayed optical feedback

NASA Astrophysics Data System (ADS)

Terrien, Soizic; Krauskopf, Bernd; Broderick, Neil G. R.; Andréoli, Louis; Selmi, Foued; Braive, Rémy; Beaudoin, Grégoire; Sagnes, Isabelle; Barbay, Sylvain

2017-10-01

A semiconductor micropillar laser with delayed optical feedback is considered. In the excitable regime, we show that a single optical perturbation can trigger a train of pulses that is sustained for a finite duration. The distribution of the pulse train duration exhibits an exponential behavior characteristic of a noise-induced process driven by uncorrelated white noise present in the system. The comparison of experimental observations with theoretical and numerical analysis of a minimal model yields excellent agreement. Importantly, the random switch-off process takes place between two attractors of different nature: an equilibrium and a periodic orbit. Our analysis shows that there is a small time window during which the pulsations are very sensitive to noise, and this explains the observed strong bias toward switch-off. These results raise the possibility of all optical control of the pulse train duration that may have an impact for practical applications in photonics and may also apply to the dynamics of other noise-driven excitable systems with delayed feedback.

GHz laser-free time-resolved transmission electron microscopy: A stroboscopic high-duty-cycle method

DOE PAGES

Qiu, Jiaqi; Zhu, Yimei; Ha, Gwanghui; ...

2015-11-10

In this study, a device and a method for producing ultrashort electron pulses with GHz repetition rates via pulsing an input direct current (dc) electron beam are provided. The device and the method are based on an electromagnetic-mechanical pulser (EMMP) that consists of a series of transverse deflecting cavities and magnetic quadrupoles. The EMMP modulates and chops the incoming dc electron beam and converts it into pico- and sub-pico-second electron pulse sequences (pulse trains) at >1 GHz repetition rates, as well as controllably manipulates the resulting pulses. Ultimately, it leads to negligible electron pulse phase-space degradation compared to the incomingmore » dc beam parameters. The temporal pulse length and repetition rate for the EMMP can be continuously tunable over wide ranges.« less

Urinary 1H Nuclear Magnetic Resonance Metabolomic Fingerprinting Reveals Biomarkers of Pulse Consumption Related to Energy-Metabolism Modulation in a Subcohort from the PREDIMED study.

PubMed

Madrid-Gambin, Francisco; Llorach, Rafael; Vázquez-Fresno, Rosa; Urpi-Sarda, Mireia; Almanza-Aguilera, Enrique; Garcia-Aloy, Mar; Estruch, Ramon; Corella, Dolores; Andres-Lacueva, Cristina

2017-04-07

Little is known about the metabolome fingerprint of pulse consumption. The study of robust and accurate biomarkers for pulse dietary assessment has great value for nutritional epidemiology regarding health benefits and their mechanisms. To characterize the fingerprinting of dietary pulses (chickpeas, lentils, and beans), spot urine samples from a subcohort from the PREDIMED study were stratified using a validated food frequency questionnaire. Urine samples of nonpulse consumers (≤4 g/day of pulse intake) and habitual pulse consumers (≥25 g/day of pulse intake) were analyzed using a 1 H nuclear magnetic resonance (NMR) metabolomics approach combined with multi- and univariate data analysis. Pulse consumption showed differences through 16 metabolites coming from (i) choline metabolism, (ii) protein-related compounds, and (iii) energy metabolism (including lower urinary glucose). Stepwise logistic regression analysis was applied to design a combined model of pulse exposure, which resulted in glutamine, dimethylamine, and 3-methylhistidine. This model was evaluated by a receiver operating characteristic curve (AUC > 90% in both training and validation sets). The application of NMR-based metabolomics to reported pulse exposure highlighted new candidates for biomarkers of pulse consumption and the impact on energy metabolism, generating new hypotheses on energy modulation. Further intervention studies will confirm these findings.

Scaling and Systems Considerations in Pulsed Inductive Thrusters

NASA Technical Reports Server (NTRS)

Polzin, Kurt A.

2007-01-01

Performance scaling in pulsed inductive thrusters is discussed in the context of previous experimental studies and modeling results. Two processes, propellant ionization and acceleration, are interconnected where overall thruster performance and operation are concerned, but they are separated here to gain physical insight into each process and arrive at quantitative criteria that should be met to address or mitigate inherent inductive thruster difficulties. The effects of preionization in lowering the discharge energy requirements relative to a case where no preionization is employed, and in influencing the location of the initial current sheet, are described. The relevant performance scaling parameters for the acceleration stage are reviewed, emphasizing their physical importance and the numerical values required for efficient acceleration. The scaling parameters are then related to the design of the pulsed power train providing current to the acceleration stage. The impact of various choices in pulsed power train and circuit topology selection are reviewed, paying special attention to how these choices mitigate or exacerbate switching, lifetime, and power consumption issues.

High-speed pulse-shape generator, pulse multiplexer

DOEpatents

Burkhart, Scott C.

2002-01-01

The invention combines arbitrary amplitude high-speed pulses for precision pulse shaping for the National Ignition Facility (NIF). The circuitry combines arbitrary height pulses which are generated by replicating scaled versions of a trigger pulse and summing them delayed in time on a pulse line. The combined electrical pulses are connected to an electro-optic modulator which modulates a laser beam. The circuit can also be adapted to combine multiple channels of high speed data into a single train of electrical pulses which generates the optical pulses for very high speed optical communication. The invention has application in laser pulse shaping for inertial confinement fusion, in optical data links for computers, telecommunications, and in laser pulse shaping for atomic excitation studies. The invention can be used to effect at least a 10.times. increase in all fiber communication lines. It allows a greatly increased data transfer rate between high-performance computers. The invention is inexpensive enough to bring high-speed video and data services to homes through a super modem.

Temporal self-splitting of optical pulses

NASA Astrophysics Data System (ADS)

Ding, Chaoliang; Koivurova, Matias; Turunen, Jari; Pan, Liuzhan

2018-05-01

We present mathematical models for temporally and spectrally partially coherent pulse trains with Laguerre-Gaussian and Hermite-Gaussian Schell-model statistics as extensions of the standard Gaussian Schell model for pulse trains. We derive propagation formulas of both classes of pulsed fields in linearly dispersive media and in temporal optical systems. It is found that, in general, both types of fields exhibit time-domain self-splitting upon propagation. The Laguerre-Gaussian model leads to multiply peaked pulses, while the Hermite-Gaussian model leads to doubly peaked pulses, in the temporal far field (in dispersive media) or at the Fourier plane of a temporal system. In both model fields the character of the self-splitting phenomenon depends both on the degree of temporal and spectral coherence and on the power spectrum of the field.

Femtochemistry in the electronic ground state: Dynamic Stark control of vibrational dynamics

NASA Astrophysics Data System (ADS)

Shu, Chuan-Cun; Thomas, Esben F.; Henriksen, Niels E.

2017-09-01

We study the interplay of vibrational and rotational excitation in a diatomic molecule due to the non-resonant dynamic Stark effect. With a fixed peak intensity, optimal Gaussian pulse durations for maximizing vibrational or rotational transitions are obtained analytically and confirmed numerically for the H2 and Cl2 molecules. In general, pulse trains or more advanced pulse shaping techniques are required in order to obtain significant vibrational excitation. To that end, we demonstrate that a high degree of selectivity between vibrational and rotational excitation is possible with a suitably phase-modulated Gaussian pulse.

Femtosecond laser-electron x-ray source

DOEpatents

Hartemann, Frederic V.; Baldis, Hector A.; Barty, Chris P.; Gibson, David J.; Rupp, Bernhard

2004-04-20

A femtosecond laser-electron X-ray source. A high-brightness relativistic electron injector produces an electron beam pulse train. A system accelerates the electron beam pulse train. The femtosecond laser-electron X-ray source includes a high intra-cavity power, mode-locked laser and an x-ray optics system.

Plasma dynamics near critical density inferred from direct measurements of laser hole boring

NASA Astrophysics Data System (ADS)

Gong, Chao; Tochitsky, Sergei Ya.; Fiuza, Frederico; Pigeon, Jeremy J.; Joshi, Chan

2016-06-01

We have used multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of C O2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. A heuristic theory is presented that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. The measured values of vHB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.

High duty cycle inverse Compton scattering X-ray source

DOE PAGES

Ovodenko, A.; Agustsson, R.; Babzien, M.; ...

2016-12-22

Inverse Compton Scattering (ICS) is an emerging compact X-ray source technology, where the small source size and high spectral brightness are of interest for multitude of applications. However, to satisfy the practical flux requirements, a high-repetition-rate ICS system needs to be developed. To this end, this article reports the experimental demonstration of a high peak brightness ICS source operating in a burst mode at 40 MHz. A pulse train interaction has been achieved by recirculating a picosecond CO 2 laser pulse inside an active optical cavity synchronized to the electron beam. The pulse train ICS performance has been characterized atmore » 5- and 15- pulses per train and compared to a single pulse operation under the same operating conditions. Lastly, with the observed near-linear X-ray photon yield gain due to recirculation, as well as noticeably higher operational reliability, the burst-mode ICS offers a great potential for practical scalability towards high duty cycles.« less

Plasma dynamics near critical density inferred from direct measurements of laser hole boring.

PubMed

Gong, Chao; Tochitsky, Sergei Ya; Fiuza, Frederico; Pigeon, Jeremy J; Joshi, Chan

2016-06-01

We have used multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, v_{HB}, of the density cavity pushed forward by a train of CO_{2} laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the v_{HB} falls rapidly as the laser pulse intensity falls at the back of the laser pulse train. A heuristic theory is presented that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. The measured values of v_{HB}, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.

High-speed multi-frame dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; DeHope, William J.; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M.

2016-02-23

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses each being of a programmable pulse duration, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has a plurality of plates. A control system having a digital sequencer controls the laser and a plurality of switching components, synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to enable programmable pulse durations and programmable inter-pulse spacings.

A low-cost programmable pulse generator for physiology and behavior

PubMed Central

Sanders, Joshua I.; Kepecs, Adam

2014-01-01

Precisely timed experimental manipulations of the brain and its sensory environment are often employed to reveal principles of brain function. While complex and reliable pulse trains for temporal stimulus control can be generated with commercial instruments, contemporary options remain expensive and proprietary. We have developed Pulse Pal, an open source device that allows users to create and trigger software-defined trains of voltage pulses with high temporal precision. Here we describe Pulse Pal’s circuitry and firmware, and characterize its precision and reliability. In addition, we supply online documentation with instructions for assembling, testing and installing Pulse Pal. While the device can be operated as a stand-alone instrument, we also provide application programming interfaces in several programming languages. As an inexpensive, flexible and open solution for temporal control, we anticipate that Pulse Pal will be used to address a wide range of instrumentation timing challenges in neuroscience research. PMID:25566051

Physiologic Waveform Analysis for Early Detection of Hemorrhage during Transport and Higher Echelon Medical Care of Combat Casualties

DTIC Science & Technology

2014-03-01

waveforms that are easier to measure than ABP (e.g., pulse oximeter waveforms); (3) a NIH SBIR Phase I proposal with Retia Medical to develop automated...the training dataset. Integrating the technique with non-invasive pulse transit time (PTT) was most effective. The integrated technique specifically...the peripheral ABP waveforms in the training dataset. These techniques included the rudimentary mean ABP technique, the classic pulse pressure times

Temporal analysis of nonresonant two-photon coherent control involving bound and dissociative molecular states

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su Jing; Chen Shaohao; Jaron-Becker, Agnieszka

We theoretically study the control of two-photon excitation to bound and dissociative states in a molecule induced by trains of laser pulses, which are equivalent to certain sets of spectral phase modulated pulses. To this end, we solve the time-dependent Schroedinger equation for the interaction of molecular model systems with an external intense laser field. Our numerical results for the temporal evolution of the population in the excited states show that, in the case of an excited dissociative state, control schemes, previously validated for the atomic case, fail due to the coupling of electronic and nuclear motion. In contrast, formore » excitation to bound states the two-photon excitation probability is controlled via the time delay and the carrier-envelope phase difference between two consecutive pulses in the train.« less

Generating coherent broadband continuum soft-x-ray radiation by attosecond ionization gating.

PubMed

Pfeifer, Thomas; Jullien, Aurélie; Abel, Mark J; Nagel, Phillip M; Gallmann, Lukas; Neumark, Daniel M; Leone, Stephen R

2007-12-10

The current paradigm of isolated attosecond pulse production requires a few-cycle pulse as the driver for high-harmonic generation that has a cosine-like electric field stabilized with respect to the peak of the pulse envelope. Here, we present simulations and experimental evidence that the production of high-harmonic light can be restricted to one or a few cycles on the leading edge of a laser pulse by a gating mechanism that employs time-dependent ionization of the conversion medium. This scheme enables the generation of broadband and tunable attosecond pulses. Instead of fixing the carrier-envelope phase to produce a cosine driver pulse, the phase becomes a control parameter for the center frequency of the attosecond pulse. A method to assess the multiplicity of attosecond pulses in the pulse train is also presented. The results of our study suggest an avenue towards relaxing the requirement of few-cycle pulses for isolated attosecond pulse generation.

Analyzing the effect of slotted foil on radiation pulse profile in a mode locked afterburner X-ray free electron laser

NASA Astrophysics Data System (ADS)

Kumar, Sandeep; Hur, Min Sup; Chung, Moses

2017-06-01

Extremely short X-ray pulses in the attosecond (as) range are important tools for ultrafast dynamics, high resolution microscopy, and nuclear dynamics study. In this paper, we numerically examine the generation of gigawatt (GW) mode-locked (ML) multichromatic X-rays using the parameters of the Pohang Accelerator Laboratory (PAL)-X-ray free electron laser (XFEL), the Korean XFEL. In this vein, we analyze the ML-FEL [Thompson and McNeil, Phys. Rev. Lett. 100, 203901 (2008)] and mode-locked afterburner (MLAB) FEL [Dunning et al., Phys. Rev. Lett. 110, 104801 (2013)] schemes on the hard X-ray beamline of the PAL-XFEL. Using the ML scheme, we numerically demonstrate a train of radiation pulses in the hard X-ray (photon energy ˜12.4 keV) with 3.5 GW power and 16 as full-width half maximum (FWHM) pulse duration. On the other hand, using the MLAB scheme, a train of radiation pulses with 3 GW power and 1 as FWHM (900 zs in RMS) pulse duration has been obtained at 12.4 keV photon energy. Both schemes generate broadband, discrete, and coherent spectrum compared to the XFEL's narrowband spectrum. Furthermore, the effect of slotted foil is also studied first time on the MLAB-FEL output. Numerical comparisons show that the temporal structure of the MLAB-FEL output can be improved significantly by the use of the slotted foil. Such short X-ray pulses at XFEL facilities will allow the studies of electron-nuclear and nuclear dynamics in atoms or molecules, and the broadband radiation will substantially improve the efficiency of the experimental techniques such as X-ray crystallography and spectroscopy, paving the way for outstanding progress in biology and material science.

Extended plasma channels created by UV laser in air and their application to control electric discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zvorykin, V. D., E-mail: zvorykin@sci.lebedev.ru; Ionin, A. A.; Levchenko, A. O.

2015-02-15

Results are presented from a series of experimental and theoretical studies on creating weakly ionized extended plasma channels in atmospheric air by 248-nm UV laser radiation and their application to control long high-voltage discharges. The main mechanisms of air ionization by UV laser pulses with durations from 100 fs to 25 ns and intensities in the ranges of 3×10{sup 11}–1.5×10{sup 13} and 3×10{sup 6}–3×10{sup 11} W/cm{sup 2}, respectively, which are below the threshold for optical gas breakdown, as well as the main relaxation processes in plasma with a density of 10{sup 9}–10{sup 17} cm{sup −3}, are considered. It is shownmore » that plasma channels in air can be efficiently created by amplitude-modulated UV pulses consisting of a train of subpicosecond pulses producing primary photoelectrons and a long UV pulse suppressing electron attachment and sustaining the density of free electrons in plasma. Different modes of the generation and amplification of trains of subterawatt subpicosecond pulses and amplitude-modulated UV pulses with an energy of several tens of joules were implemented on the GARPUN-MTW hybrid Ti:sapphire-KrF laser facility. The filamentation of such UV laser beams during their propagation in air over distances of up to 100 m and the parameters of the corresponding plasma channels were studied experimentally and theoretically. Laser initiation of high-voltage electric discharges and control of their trajectories by means of amplitude-modulated UV pulses, as well as the spatiotemporal structure of breakdowns in air gaps with length of up to 80 cm, were studied.« less

Generation and manipulation of attosecond light pulses

NASA Astrophysics Data System (ADS)

Gaarde, Mette

2006-05-01

Attosecond pulses of light can be generated in the extremely non-linear interactions between an ultrashort, intense laser pulse and a gas of atoms, via the process of high harmonic generation [1,2]. In one approach, a number of odd harmonics of rougly equal strength are combined to form a train of sub-femtosecond pulses. If the harmonics are locked in phase to each other, the train will consist of the emission of one attosecond pulse every half cycle of the driving laser field [1,3]. It is in general not trivial to ensure that the harmonics are phase-locked as they are generated with intrinsically different phases. These phases originate in the strong field dynamics of the light-matter interaction [4].We will discuss different ways of generating and manipulating attosecond pulses via high harmonic generation. We will show how the harmonics can be phase-locked and better synchronized so as to form optimal pulse trains [3]. We will also show that it is possible to generate trains of pulses separated by a full laser cycle, by combining the driving laser field with its second harmonic [5]. The strong field continuum dynamics driven by the two-color field is very different from that of the one-color field and varies strongly with the delay between the two laser fields [6]. (1) P. M. Paul et al, Science 292, 1689 (2001).(2) M. Hentschel et al, Nature 414, 509 (2001).(3) R. Lopez-Martens et al, PRL 94, 033001 (2005).(4) P. Antoine, A. L'Huillier, and M. Lewenstein, PRL 77, 1234 (1996).(5) J. Mauritsson et al, in preparation (2006).(6) M. B. Gaarde et al, in preparation (2006).

The effect of call libraries and acoustic filters on the identification of bat echolocation.

PubMed

Clement, Matthew J; Murray, Kevin L; Solick, Donald I; Gruver, Jeffrey C

2014-09-01

Quantitative methods for species identification are commonly used in acoustic surveys for animals. While various identification models have been studied extensively, there has been little study of methods for selecting calls prior to modeling or methods for validating results after modeling. We obtained two call libraries with a combined 1556 pulse sequences from 11 North American bat species. We used four acoustic filters to automatically select and quantify bat calls from the combined library. For each filter, we trained a species identification model (a quadratic discriminant function analysis) and compared the classification ability of the models. In a separate analysis, we trained a classification model using just one call library. We then compared a conventional model assessment that used the training library against an alternative approach that used the second library. We found that filters differed in the share of known pulse sequences that were selected (68 to 96%), the share of non-bat noises that were excluded (37 to 100%), their measurement of various pulse parameters, and their overall correct classification rate (41% to 85%). Although the top two filters did not differ significantly in overall correct classification rate (85% and 83%), rates differed significantly for some bat species. In our assessment of call libraries, overall correct classification rates were significantly lower (15% to 23% lower) when tested on the second call library instead of the training library. Well-designed filters obviated the need for subjective and time-consuming manual selection of pulses. Accordingly, researchers should carefully design and test filters and include adequate descriptions in publications. Our results also indicate that it may not be possible to extend inferences about model accuracy beyond the training library. If so, the accuracy of acoustic-only surveys may be lower than commonly reported, which could affect ecological understanding or management decisions based on acoustic surveys.

The effect of call libraries and acoustic filters on the identification of bat echolocation

PubMed Central

Clement, Matthew J; Murray, Kevin L; Solick, Donald I; Gruver, Jeffrey C

2014-01-01

Quantitative methods for species identification are commonly used in acoustic surveys for animals. While various identification models have been studied extensively, there has been little study of methods for selecting calls prior to modeling or methods for validating results after modeling. We obtained two call libraries with a combined 1556 pulse sequences from 11 North American bat species. We used four acoustic filters to automatically select and quantify bat calls from the combined library. For each filter, we trained a species identification model (a quadratic discriminant function analysis) and compared the classification ability of the models. In a separate analysis, we trained a classification model using just one call library. We then compared a conventional model assessment that used the training library against an alternative approach that used the second library. We found that filters differed in the share of known pulse sequences that were selected (68 to 96%), the share of non-bat noises that were excluded (37 to 100%), their measurement of various pulse parameters, and their overall correct classification rate (41% to 85%). Although the top two filters did not differ significantly in overall correct classification rate (85% and 83%), rates differed significantly for some bat species. In our assessment of call libraries, overall correct classification rates were significantly lower (15% to 23% lower) when tested on the second call library instead of the training library. Well-designed filters obviated the need for subjective and time-consuming manual selection of pulses. Accordingly, researchers should carefully design and test filters and include adequate descriptions in publications. Our results also indicate that it may not be possible to extend inferences about model accuracy beyond the training library. If so, the accuracy of acoustic-only surveys may be lower than commonly reported, which could affect ecological understanding or management decisions based on acoustic surveys. PMID:25535563

The effect of call libraries and acoustic filters on the identification of bat echolocation

USGS Publications Warehouse

Clement, Matthew; Murray, Kevin L; Solick, Donald I; Gruver, Jeffrey C

2014-01-01

Quantitative methods for species identification are commonly used in acoustic surveys for animals. While various identification models have been studied extensively, there has been little study of methods for selecting calls prior to modeling or methods for validating results after modeling. We obtained two call libraries with a combined 1556 pulse sequences from 11 North American bat species. We used four acoustic filters to automatically select and quantify bat calls from the combined library. For each filter, we trained a species identification model (a quadratic discriminant function analysis) and compared the classification ability of the models. In a separate analysis, we trained a classification model using just one call library. We then compared a conventional model assessment that used the training library against an alternative approach that used the second library. We found that filters differed in the share of known pulse sequences that were selected (68 to 96%), the share of non-bat noises that were excluded (37 to 100%), their measurement of various pulse parameters, and their overall correct classification rate (41% to 85%). Although the top two filters did not differ significantly in overall correct classification rate (85% and 83%), rates differed significantly for some bat species. In our assessment of call libraries, overall correct classification rates were significantly lower (15% to 23% lower) when tested on the second call library instead of the training library. Well-designed filters obviated the need for subjective and time-consuming manual selection of pulses. Accordingly, researchers should carefully design and test filters and include adequate descriptions in publications. Our results also indicate that it may not be possible to extend inferences about model accuracy beyond the training library. If so, the accuracy of acoustic-only surveys may be lower than commonly reported, which could affect ecological understanding or management decisions based on acoustic surveys.

Large-area tungsten disulfide for ultrafast photonics.

PubMed

Yan, Peiguang; Chen, Hao; Yin, Jinde; Xu, Zihan; Li, Jiarong; Jiang, Zike; Zhang, Wenfei; Wang, Jinzhang; Li, Irene Ling; Sun, Zhipei; Ruan, Shuangchen

2017-02-02

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have attracted significant interest in various optoelectronic applications due to their excellent nonlinear optical properties. One of the most important applications of TMDs is to be employed as an extraordinary optical modulation material (e.g., the saturable absorber (SA)) in ultrafast photonics. The main challenge arises while embedding TMDs into fiber laser systems to generate ultrafast pulse trains and thus constraints their practical applications. Herein, few-layered WS 2 with a large-area was directly transferred on the facet of the pigtail and acted as a SA for erbium-doped fiber laser (EDFL) systems. In our study, WS 2 SA exhibited remarkable nonlinear optical properties (e.g., modulation depth of 15.1% and saturable intensity of 157.6 MW cm -2 ) and was used for ultrafast pulse generation. The soliton pulses with remarkable performances (e.g., ultrashort pulse duration of 1.49 ps, high stability of 71.8 dB, and large pulse average output power of 62.5 mW) could be obtained in a telecommunication band. To the best of our knowledge, the average output power of the mode-locked pulse trains is the highest by employing TMD materials in fiber laser systems. These results indicate that atomically large-area WS 2 could be used as excellent optical modulation materials in ultrafast photonics.

Partial tripolar cochlear implant stimulation: Spread of excitation and forward masking in the inferior colliculus.

PubMed

Bierer, Julie Arenberg; Bierer, Steven M; Middlebrooks, John C

2010-12-01

This study examines patterns of neural activity in response to single biphasic electrical pulses, presented alone or following a forward masking pulse train, delivered by a cochlear implant. Recordings were made along the tonotopic axis of the central nucleus of the inferior colliculus (ICC) in ketamine/xylazine anesthetized guinea pigs. The partial tripolar electrode configuration was used, which provided a systematic way to vary the tonotopic extent of ICC activation between monopolar (broad) and tripolar (narrow) extremes while maintaining the same peak of activation. The forward masking paradigm consisted of a 200 ms masker pulse train (1017 pulses per second) followed 10 ms later by a single-pulse probe stimulus; the current fraction of the probe was set to 0 (monopolar), 1 (tripolar), or 0.5 (hybrid), and the fraction of the masker was fixed at 0.5. Forward masking tuning profiles were derived from the amount of masking current required to just suppress the activity produced by a fixed-level probe. These profiles were sharper for more focused probe configurations, approximating the pattern of neural activity elicited by single (non-masked) pulses. The result helps to bridge the gap between previous findings in animals and recent psychophysical data. Copyright © 2010 Elsevier B.V. All rights reserved.

Partial tripolar cochlear implant stimulation: Spread of excitation and forward masking in the inferior colliculus

PubMed Central

Bierer, Julie Arenberg; Bierer, Steven M.; Middlebrooks, John C.

2010-01-01

This study examines patterns of neural activity in response to single biphasic electrical pulses, presented alone or following a forward masking pulse train, delivered by a cochlear implant. Recordings were made along the tonotopic axis of the central nucleus of the inferior colliculus (ICC) in ketamine/xylazine anesthetized guinea pigs. The partial tripolar electrode configuration was used, which provided a systematic way to vary the tonotopic extent of ICC activation between monopolar (broad) and tripolar (narrow) extremes while maintaining the same peak of activation. The forward masking paradigm consisted of a 200-ms masker pulse train (1017 pulses per second) followed 10 ms later by a single-pulse probe stimulus; the current fraction of the probe was set to 0 (monopolar), 1 (tripolar), or 0.5 (hybrid), and the fraction of the masker was fixed at 0.5. Forward masking tuning profiles were derived from the amount of masking current required to just suppress the activity produced by a fixed-level probe. These profiles were sharper for more focused probe configurations, approximating the pattern of neural activity elicited by single (non-masked) pulses. The result helps to bridge the gap between previous findings in animals and recent psychophysical data. PMID:20727397

Exploiting solitons in all-optical networks

NASA Astrophysics Data System (ADS)

Atieh, Ahmad K.

Two key components, the pulse generator and optical signal demultiplexer, needed for the implementation of all-optical soliton-based local area and wide area networks are investigated. The technology of generating a bright soliton pulse train from a sinusoidal pulse train produced as the beat signal of two distributed feedback laser diodes passed through a so-called comblike fiber structure is developed. A design methodology for this structure is discussed, and using this approach a soliton pulse source is constructed generating 1553 nm pulses at a repetition rate of 50 GHz, with pulses of full width at half maximum of 2.0 ps. The fiber structure used to generate the bright soliton pulse train employs the lowest average power for the beat signal ever reported in the literature, and the shortest length of fiber. The same structure (with a different design) is also used to produce a 47.6 GHz dark soliton pulse train with a full width at half maximum of 3.8 ps. This is the first reported use of this structure to generate dark solitons. It is shown that the comblike dispersion profile fiber structures may also be exploited for soliton pulse compression producing widths as short as 200 fs. Two approaches to implementation of optical signal demultiplexing are discussed. These are the nonlinear optical loop mirror (NOLM) and the separation of multilevel time division multiplexed signal pulses in the frequency domain by exploiting the relationship between the pulse's energy (i.e. pulse amplitude and width) and the Raman self-frequency shift. A modification of the NOLM scheme is investigated where feedback that adjusts the power of the control signal (by controlling the gain of an erbium-doped fiber amplifier introduced into the control signal input path) is employed to make the structure insensitive to the state of polarization of the signal and control pulses. In order to better understand the physical phenomena exploited in optical fiber soliton transmission and the above schemes, two experiments are conducted to measure the fiber nonlinear ratio (n2/Aeff) and the Raman time constant (TR) in single-mode fibers at 1550 nm. The fiber nonlinear ratio was measured for standard telecommunication fiber, dispersion shifted fiber, and dispersion compensating fiber. A value of 3.0 fs for the Raman time constant was measured and is recommended for soliton pulse propagation modeling in single-mode optical fibers.

Anisotropy modulations of femtosecond laser pulse induced periodic surface structures on silicon by adjusting double pulse delay.

PubMed

Han, Weina; Jiang, Lan; Li, Xiaowei; Wang, Qingsong; Li, Hao; Lu, YongFeng

2014-06-30

We demonstrate that the polarization-dependent anisotropy of the laser-induced periodic surface structure (LIPSS) on silicon can be adjusted by designing a femtosecond laser pulse train (800 nm, 50 fs, 1 kHz). By varying the pulse delay from 100 to 1600 fs within a double pulse train to reduce the deposited pulse energy, which weakens the directional surface plasmon polarition (SPP)-laser energy coupling based on the initial formed ripple structure, the polarization-dependent geometrical morphology of the LIPSS evolves from a nearly isotropic circular shape to a somewhat elongated elliptical shape. Meanwhile, the controllable anisotropy of the two-dimensional scanned-line widths with different directions is achieved based on a certain pulse delay combined with the scanning speed. This can effectively realize better control over large-area uniform LIPSS formation. As an example, we further show that the large-area LIPSS can be formed with different scanning times under different pulse delays.

Advances in generation of high-repetition-rate burst mode laser output.

PubMed

Jiang, Naibo; Webster, Matthew C; Lempert, Walter R

2009-02-01

It is demonstrated that the incorporation of variable pulse duration flashlamp power supplies into an Nd:YAG burst mode laser system results in very substantial increases in the realizable energy per pulse, the total pulse train length, and uniformity of the intensity envelope. As an example, trains of 20 pulses at burst frequencies of 50 and 20 kHz are demonstrated with individual pulse energy at 1064 nm of 220 and 400 mJ, respectively. Conversion efficiency to the second- (532 nm) and third- (355 nm) harmonic wavelengths of approximately 50% and 35-40%, respectively, is also achieved. Use of the third-harmonic output of the burst mode laser as a pump source for a simple, home built optical parametric oscillator (OPO) produces pulse trains of broadly wavelength tunable output. Sum-frequency mixing of OPO signal output at 622 nm with residual output from the 355 nm pump beam is shown to produce uniform bursts of tunable output at approximately 226 nm, with individual pulse energy of approximately 0.5 mJ. Time-correlated NO planar laser induced fluorescence (PLIF) image sequences are obtained in a Mach 3 wind tunnel at 500 kHz, representing, to our knowledge, the first demonstration of NO PLIF imaging at repetition rates exceeding tens of hertz.

Frequency-modulated orocutaneous stimulation promotes non-nutritive suck development in preterm infants with respiratory distress syndrome or chronic lung disease.

PubMed

Barlow, S M; Lee, J; Wang, J; Oder, A; Hall, S; Knox, K; Weatherstone, K; Thompson, D

2014-02-01

For the premature infant, extrauterine life is a pathological condition, which greatly amplifies the challenges to the brain in establishing functional oromotor behaviors. The extent to which suck can be entrained using a synthetically patterned orocutaneous input to promote its development in preterm infants who manifest chronic lung disease (CLD) is unknown. The objective of this study was to evaluate the effects of a frequency-modulated (FM) orocutaneous pulse train delivered through a pneumatically charged pacifier capable of enhancing non-nutritive suck (NNS) activity in tube-fed premature infants. A randomized trial to evaluate the efficacy of pneumatic orocutaneous stimulation 3 × per day on NNS development and length of stay (LOS) in the neonatal intensive care unit among 160 newborn infants distributed among three sub-populations, including healthy preterm infants, respiratory distress syndrome (RDS) and CLD. Study infants received a regimen of orocutaneous pulse trains through a PULSED pressurized silicone pacifier or a SHAM control (blind pacifier) during gavage feeds for up to 10 days. Mixed modeling, adjusted for the infant's gender, gestational age, postmenstrual age and birth weight, was used to handle interdependency among repeated measures within subjects. A significant main effect for stimulation mode (SHAM pacifier vs PULSED orosensory) was found among preterm infants for NNS bursts per min (P=0.003), NNS events per min (P=0.033) and for total oral compressions per min (NNS+nonNNS) (P=0.016). Pairwise comparison of adjusted means using Bonferroni adjustment indicated RDS and CLD infants showed the most significant gains on these NNS performance indices. CLD infants in the treatment group showed significantly shorter LOS by an average of 2.5 days. FM PULSED orocutaneous pulse train stimuli delivered through a silicone pacifier are effective in facilitating NNS burst development in tube-fed RDS and CLD preterm infants, with an added benefit of reduced LOS for CLD infants.

Generation of a femtosecond electron microbunch train from a photocathode using twofold Michelson interferometer

NASA Astrophysics Data System (ADS)

Shevelev, M.; Aryshev, A.; Terunuma, N.; Urakawa, J.

2017-10-01

The interest in producing ultrashort electron bunches has risen sharply among scientists working on the design of high-gradient wakefield accelerators. One attractive approach generating electron bunches is to illuminate a photocathode with a train of femtosecond laser pulses. In this paper we describe the design and testing of a laser system for an rf gun based on a commercial titanium-sapphire laser technology. The technology allows the production of four femtosecond laser pulses with a continuously variable pulse delay. We also use the designed system to demonstrate the experimental generation of an electron microbunch train obtained by illuminating a cesium-telluride semiconductor photocathode. We use conventional diagnostics to characterize the electron microbunches produced and confirm that it may be possible to control the main parameter of an electron microbunch train.

Femtosecond laser-induced periodic structure adjustments based on electron dynamics control: from subwavelength ripples to double-grating structures.

PubMed

Shi, Xuesong; Jiang, Lan; Li, Xin; Wang, Sumei; Yuan, Yanping; Lu, Yongfeng

2013-10-01

This study proposes a method for adjusting subwavelength ripple periods and the corresponding double-grating structures formed on fused silica by designing femtosecond laser pulse trains based on localized transient electron density control. Four near-constant period ranges of 190-490 nm of ripples perpendicular to the polarization are obtained by designing pulse trains to excite and modulate the surface plasmon waves. In the period range of 350-490 nm, the double-grating structure is fabricated in one step, which is probably attributable to the grating-assisted enhanced energy deposition and subsequent thermal effects.

Coherent combining of pulsed fiber amplifiers in the nonlinear chirp regime with intra-pulse phase control.

PubMed

Palese, Stephen; Cheung, Eric; Goodno, Gregory; Shih, Chun-Ching; Di Teodoro, Fabio; McComb, Timothy; Weber, Mark

2012-03-26

Two high pulse contrast (> 95 dB) polarization maintaining all-fiber amplifier chains were coherently combined to generate 0.42 mJ, 1 ns 25 kHz pulses with 79% efficiency despite 38 radians of intra-pulse phase distortion. A recursive intra-pulse phase compensation method was utilized to correct for the large nonlinear chirp providing a path for improved coherent waveform control of nanosecond pulse trains.

Spike Train Similarity Space (SSIMS) Method Detects Effects of Obstacle Proximity and Experience on Temporal Patterning of Bat Biosonar

PubMed Central

Accomando, Alyssa W.; Vargas-Irwin, Carlos E.; Simmons, James A.

2018-01-01

Bats emit biosonar pulses in complex temporal patterns that change to accommodate dynamic surroundings. Efforts to quantify these patterns have included analyses of inter-pulse intervals, sonar sound groups, and changes in individual signal parameters such as duration or frequency. Here, the similarity in temporal structure between trains of biosonar pulses is assessed. The spike train similarity space (SSIMS) algorithm, originally designed for neural activity pattern analysis, was applied to determine which features of the environment influence temporal patterning of pulses emitted by flying big brown bats, Eptesicus fuscus. In these laboratory experiments, bats flew down a flight corridor through an obstacle array. The corridor varied in width (100, 70, or 40 cm) and shape (straight or curved). Using a relational point-process framework, SSIMS was able to discriminate between echolocation call sequences recorded from flights in each of the corridor widths. SSIMS was also able to tell the difference between pulse trains recorded during flights where corridor shape through the obstacle array matched the previous trials (fixed, or expected) as opposed to those recorded from flights with randomized corridor shape (variable, or unexpected), but only for the flight path shape in which the bats had previous training. The results show that experience influences the temporal patterns with which bats emit their echolocation calls. It is demonstrated that obstacle proximity to the bat affects call patterns more dramatically than flight path shape. PMID:29472848

Spike Train Similarity Space (SSIMS) Method Detects Effects of Obstacle Proximity and Experience on Temporal Patterning of Bat Biosonar.

PubMed

Accomando, Alyssa W; Vargas-Irwin, Carlos E; Simmons, James A

2018-01-01

Bats emit biosonar pulses in complex temporal patterns that change to accommodate dynamic surroundings. Efforts to quantify these patterns have included analyses of inter-pulse intervals, sonar sound groups, and changes in individual signal parameters such as duration or frequency. Here, the similarity in temporal structure between trains of biosonar pulses is assessed. The spike train similarity space (SSIMS) algorithm, originally designed for neural activity pattern analysis, was applied to determine which features of the environment influence temporal patterning of pulses emitted by flying big brown bats, Eptesicus fuscus . In these laboratory experiments, bats flew down a flight corridor through an obstacle array. The corridor varied in width (100, 70, or 40 cm) and shape (straight or curved). Using a relational point-process framework, SSIMS was able to discriminate between echolocation call sequences recorded from flights in each of the corridor widths. SSIMS was also able to tell the difference between pulse trains recorded during flights where corridor shape through the obstacle array matched the previous trials (fixed, or expected) as opposed to those recorded from flights with randomized corridor shape (variable, or unexpected), but only for the flight path shape in which the bats had previous training. The results show that experience influences the temporal patterns with which bats emit their echolocation calls. It is demonstrated that obstacle proximity to the bat affects call patterns more dramatically than flight path shape.

Effects of short-term resistance training and pulsed electromagnetic fields on bone metabolism and joint function in severe haemophilia A patients with osteoporosis: a randomized controlled trial.

PubMed

Parhampour, Behrouz; Torkaman, Giti; Hoorfar, Hamid; Hedayati, Mehdi; Ravanbod, Roya

2014-05-01

To assess the effects of short-term resistance training and pulsed electromagnetic fields on bone metabolism and joint function in patients with haemophilia with osteoporosis. A randomized, controlled, patient and blood sample assessor-blinded, six-week trial, three times weekly. Hospital outpatients with severe haemophilia A and osteoporosis. Forty-eight patients were randomly assigned to resistance training (RT, n = 13), combined resistance training with pulsed electromagnetic fields (RTPEMF, n = 12), pulsed electromagnetic fields (PEMF, n = 11) and control (n = 12) groups. The RT group received 30-40 minutes of resistance exercises and placebo pulsed electromagnetic fields. The RTPEMF group received the same exercises with lower repetition and 30 minutes of pulsed electromagnetic fields. The PEMF group was exposed to 60 minutes of pulsed electromagnetic fields (30 Hz and 40 Gauss). Bone-specific alkaline phosphatase, N-terminal telopeptide of type 1 collagen, and joint function, using the modified Colorado Questionnaire, were measured before and after the programme. The absolute change of bone-specific alkaline phosphatase was significant in the RT and RTPEMF groups compared with the control group (25.41 ± 14.40, 15.09 ± 5.51, and -4.73 ± 2.93 U/L, respectively). The absolute changes in the total score for joint function were significant for knees, ankles, and elbows in the RT group (9.2 ± 1.38, 5.1 ± 0.5, and 3.2 ± 0.8, respectively) and the RTPEMF group (7.7 ± 1.0, 3.3 ± 0.6, and 2.5 ± 0.7, respectively) compared to the PEMF and control groups. This value was significant for knee joints in the PEMF group compared to the control group (3.4 ± 0.5 and 0.66 ± 0.4, respectively). Resistance training is effective for improving bone formation and joint function in severe haemophilia A patients with osteoporosis.

Analysis of fatigue characteristic of sm-substituted DyFeCo magneto-optical films

NASA Astrophysics Data System (ADS)

Li, Zuoyi; Wang, Ke; Yang, Xiaofei; Li, Zhen; Lin, Gengqi

2003-04-01

The fatigue characteristic of the amorphous Sm-substituted DyFeCo magneto-optical alloy films fabricated by R.F. magnetron sputtering method were investigated by accelerated pulse training method under the condition of magnetic field modulation plus laser pulse irradiation. The evaluation of fatigue characteristic is determined from the static magneto-optical signal readout level after several writing/erasing repetitions compared with initial level. The experimental dependence of fatigue characteristics is in good agreement with the model based on the JMA equation. Furthermore, the Avrami factor can be derived from the model. Experimental results show that it is very effective in studying the writing/erasing ability of magneto-optical films employed the method of combined the accelerated pulse training with the JMA equation and Sm-substituted HRE-TM alloys can act as a practical medium for MO storage at short wavelength.

Fast and slow light generated by surface plasmon wave and gold grating coupling effects

NASA Astrophysics Data System (ADS)

Amiri, Iraj S.; Ariannejad, M. M.; Tajdidzadeh, M.; Sorger, Volker J.; Ling, Xi; Yupapin, P.

2018-06-01

We present here the results of a simulation of the effect of gold and graphene coatings on silicon micro-ring resonators. We studied the effect of different radii of graphene on the time delay, from which one an interesting aspect of light pulse behaviors, such as fast light, was numerically investigated. The obtained results indicate that the time delay can be varied, which is in good agreement with theoretical predictions. Fast and slow light pulse trains can be obtained by modifying the throughput port, which forms the gold grating length. The temporal gaps between the fast and slow light in the used graphene and gold are 140 and 168 fs, respectively, which can be tuned by varying the radius or grating length. The obtained results show that such a device may be useful in applications requiring fast and slow light pulse train pairs, such as optical switching, sensors, communications, and security applications.

Fast and slow light generated by surface plasmon wave and gold grating coupling effects

NASA Astrophysics Data System (ADS)

Amiri, Iraj S.; Ariannejad, M. M.; Tajdidzadeh, M.; Sorger, Volker J.; Ling, Xi; Yupapin, P.

2018-01-01

We present here the results of a simulation of the effect of gold and graphene coatings on silicon micro-ring resonators. We studied the effect of different radii of graphene on the time delay, from which one an interesting aspect of light pulse behaviors, such as fast light, was numerically investigated. The obtained results indicate that the time delay can be varied, which is in good agreement with theoretical predictions. Fast and slow light pulse trains can be obtained by modifying the throughput port, which forms the gold grating length. The temporal gaps between the fast and slow light in the used graphene and gold are 140 and 168 fs, respectively, which can be tuned by varying the radius or grating length. The obtained results show that such a device may be useful in applications requiring fast and slow light pulse train pairs, such as optical switching, sensors, communications, and security applications.

Short optical pulse generation at 40 GHz with a bulk electro-absorption modulator packaged device

NASA Astrophysics Data System (ADS)

Langlois, Patrick; Moore, Ronald; Prosyk, Kelvin; O'Keefe, Sean; Oosterom, Jill A.; Betty, Ian; Foster, Robert; Greenspan, Jonathan; Singh, Priti

2003-12-01

Short optical pulse generation at 40GHz and 1540nm wavelength is achieved using fully packaged bulk quaternary electro-absorption modulator modules. Experimental results obtained with broadband and narrowband optimized packaged modules are presented and compared against empirical model predictions. Pulse duty cycle, extinction ratio and chirp are studied as a function of sinusoidal drive voltage and detuning between operating wavelength and modulator absorption band edge. Design rules and performance trade-offs are discussed. Low-chirp pulses with a FWHM of ~12ps and sub-4ps at a rate of 40GHz are demonstrated. Optical time-domain demultiplexing of a 40GHz to a 10GHz pulse train is also demonstrated with better than 20dB extinction ratio.

Responses to amplitude modulated infrared stimuli in the guinea pig inferior colliculus

NASA Astrophysics Data System (ADS)

Richter, Claus-Peter; Young, Hunter

2013-03-01

Responses of units in the central nucleus of the inferior colliculus of the guinea pig were recorded with tungsten electrodes. The set of data presented here is limited to high stimulus levels. The effect of changing the modulation frequency and the modulation depth was explored for acoustic and laser stimuli. The selected units responded to sinusoidal amplitude modulated (AM) tones, AM trains of clicks, and AM trains of laser pulses with a modulation of their spike discharge. At modulation frequencies of 20 Hz, some units tended to respond with 40 Hz to the acoustic stimuli, but only at 20 Hz for the trains of laser pulses. For all modes of stimulation the responses revealed a dominant response to the first cycle of the modulation, with decreasing number of action potential during successive cycles. While amplitude modulated tone bursts and amplitude modulated trains of acoustic clicks showed similar patterns, the response to trains of laser pulses was different.

High-speed multiframe dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; DeHope, William J.; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M.

2015-10-20

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses of a predefined pulse duration and waveform, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has two pairs of plates arranged perpendicular to one another. A control system controls the laser and a plurality of switching components synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to be provided with an independently set duration and independently set inter-pulse spacings.

High-speed multiframe dynamic transmission electron microscope image acquisition system with arbitrary timing

DOEpatents

Reed, Bryan W.; Dehope, William J; Huete, Glenn; LaGrange, Thomas B.; Shuttlesworth, Richard M

2016-06-21

An electron microscope is disclosed which has a laser-driven photocathode and an arbitrary waveform generator (AWG) laser system ("laser"). The laser produces a train of temporally-shaped laser pulses of a predefined pulse duration and waveform, and directs the laser pulses to the laser-driven photocathode to produce a train of electron pulses. An image sensor is used along with a deflector subsystem. The deflector subsystem is arranged downstream of the target but upstream of the image sensor, and has two pairs of plates arranged perpendicular to one another. A control system controls the laser and a plurality of switching components synchronized with the laser, to independently control excitation of each one of the deflector plates. This allows each electron pulse to be directed to a different portion of the image sensor, as well as to be provided with an independently set duration and independently set inter-pulse spacings.

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

NASA Astrophysics Data System (ADS)

Faatz, B.; Plönjes, E.; Ackermann, S.; Agababyan, A.; Asgekar, V.; Ayvazyan, V.; Baark, S.; Baboi, N.; Balandin, V.; von Bargen, N.; Bican, Y.; Bilani, O.; Bödewadt, J.; Böhnert, M.; Böspflug, R.; Bonfigt, S.; Bolz, H.; Borges, F.; Borkenhagen, O.; Brachmanski, M.; Braune, M.; Brinkmann, A.; Brovko, O.; Bruns, T.; Castro, P.; Chen, J.; Czwalinna, M. K.; Damker, H.; Decking, W.; Degenhardt, M.; Delfs, A.; Delfs, T.; Deng, H.; Dressel, M.; Duhme, H.-T.; Düsterer, S.; Eckoldt, H.; Eislage, A.; Felber, M.; Feldhaus, J.; Gessler, P.; Gibau, M.; Golubeva, N.; Golz, T.; Gonschior, J.; Grebentsov, A.; Grecki, M.; Grün, C.; Grunewald, S.; Hacker, K.; Hänisch, L.; Hage, A.; Hans, T.; Hass, E.; Hauberg, A.; Hensler, O.; Hesse, M.; Heuck, K.; Hidvegi, A.; Holz, M.; Honkavaara, K.; Höppner, H.; Ignatenko, A.; Jäger, J.; Jastrow, U.; Kammering, R.; Karstensen, S.; Kaukher, A.; Kay, H.; Keil, B.; Klose, K.; Kocharyan, V.; Köpke, M.; Körfer, M.; Kook, W.; Krause, B.; Krebs, O.; Kreis, S.; Krivan, F.; Kuhlmann, J.; Kuhlmann, M.; Kube, G.; Laarmann, T.; Lechner, C.; Lederer, S.; Leuschner, A.; Liebertz, D.; Liebing, J.; Liedtke, A.; Lilje, L.; Limberg, T.; Lipka, D.; Liu, B.; Lorbeer, B.; Ludwig, K.; Mahn, H.; Marinkovic, G.; Martens, C.; Marutzky, F.; Maslocv, M.; Meissner, D.; Mildner, N.; Miltchev, V.; Molnar, S.; Mross, D.; Müller, F.; Neumann, R.; Neumann, P.; Nölle, D.; Obier, F.; Pelzer, M.; Peters, H.-B.; Petersen, K.; Petrosyan, A.; Petrosyan, G.; Petrosyan, L.; Petrosyan, V.; Petrov, A.; Pfeiffer, S.; Piotrowski, A.; Pisarov, Z.; Plath, T.; Pototzki, P.; Prandolini, M. J.; Prenting, J.; Priebe, G.; Racky, B.; Ramm, T.; Rehlich, K.; Riedel, R.; Roggli, M.; Röhling, M.; Rönsch-Schulenburg, J.; Rossbach, J.; Rybnikov, V.; Schäfer, J.; Schaffran, J.; Schlarb, H.; Schlesselmann, G.; Schlösser, M.; Schmid, P.; Schmidt, C.; Schmidt-Föhre, F.; Schmitz, M.; Schneidmiller, E.; Schöps, A.; Scholz, M.; Schreiber, S.; Schütt, K.; Schütz, U.; Schulte-Schrepping, H.; Schulz, M.; Shabunov, A.; Smirnov, P.; Sombrowski, E.; Sorokin, A.; Sparr, B.; Spengler, J.; Staack, M.; Stadler, M.; Stechmann, C.; Steffen, B.; Stojanovic, N.; Sychev, V.; Syresin, E.; Tanikawa, T.; Tavella, F.; Tesch, N.; Tiedtke, K.; Tischer, M.; Treusch, R.; Tripathi, S.; Vagin, P.; Vetrov, P.; Vilcins, S.; Vogt, M.; de Zubiaurre Wagner, A.; Wamsat, T.; Weddig, H.; Weichert, G.; Weigelt, H.; Wentowski, N.; Wiebers, C.; Wilksen, T.; Willner, A.; Wittenburg, K.; Wohlenberg, T.; Wortmann, J.; Wurth, W.; Yurkov, M.; Zagorodnov, I.; Zemella, J.

2016-06-01

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.

HIGH POWER PULSED OSCILLATOR

DOEpatents

Singer, S.; Neher, L.K.

1957-09-24

A high powered, radio frequency pulse oscillator is described for generating trains of oscillations at the instant an input direct voltage is impressed, or immediately upon application of a light pulse. In one embodiment, the pulse oscillator comprises a photo-multiplier tube with the cathode connected to the first dynode by means of a resistor, and adjacent dynodes are connected to each other through adjustable resistors. The ohmage of the resistors progressively increases from a very low value for resistors adjacent the cathode to a high value adjacent the plate, the last dynode. Oscillation occurs with this circuit when a high negative voltage pulse is applied to the cathode and the photo cathode is bombarded. Another embodiment adds capacitors at the resistor connection points of the above circuit to increase the duration of the oscillator train.

Stability of the mode-locking regime in tapered quantum-dot lasers

NASA Astrophysics Data System (ADS)

Bardella, P.; Drzewietzki, L.; Rossetti, M.; Weber, C.; Breuer, S.

2018-02-01

We study numerically and experimentally the role of the injection current and reverse bias voltage on the pulse stability of tapered, passively mode-locked, Quantum Dot (QD) lasers. By using a multi-section delayed differential equation and introducing in the model the QD inhomogenous broadening, we are able to predict the onset of leading and trailing edge instabilities in the emitted pulse trains and to identify specific trends of stability in dependence on the laser biasing conditions. The numerical results are confirmed experimentally trough amplitude and timing stability analysis of the pulses.

Diffraction leveraged modulation of X-ray pulses using MEMS-based X-ray optics

DOEpatents

Lopez, Daniel; Shenoy, Gopal; Wang, Jin; Walko, Donald A.; Jung, Il-Woong; Mukhopadhyay, Deepkishore

2016-08-09

A method and apparatus are provided for implementing Bragg-diffraction leveraged modulation of X-ray pulses using MicroElectroMechanical systems (MEMS) based diffractive optics. An oscillating crystalline MEMS device generates a controllable time-window for diffraction of the incident X-ray radiation. The Bragg-diffraction leveraged modulation of X-ray pulses includes isolating a particular pulse, spatially separating individual pulses, and spreading a single pulse from an X-ray pulse-train.

Chronic lithium treatment rectifies maladaptive dopamine release in the nucleus accumbens.

PubMed

Can, Adem; Frost, Douglas O; Cachope, Roger; Cheer, Joseph F; Gould, Todd D

2016-11-01

Chronic lithium treatment effectively reduces behavioral phenotypes of mania in humans and rodents. The mechanisms by which lithium exerts these actions are poorly understood. Pre-clinical and clinical evidence have implicated increased mesolimbic dopamine (DA) neurotransmission with mania. We used fast-scan cyclic voltammetry to characterize changes in extracellular DA concentrations in the nucleus accumbens (NAc) core evoked by 20 and 60 Hz electrical stimulation of the ventral tegmental area (VTA) in C57BL6/J mice treated either acutely or chronically with lithium. The effects of chronic lithium treatment on the availability of DA for release were assessed by depleting readily releasable DA using short inter-train intervals, or administering d-amphetamine acutely to mobilize readily releasable DA. Chronic, but not acute, lithium treatment decreased the amplitude of DA responses in the NAc following 60 Hz pulse train stimulation. Neither lithium treatment altered the kinetics of DA release or reuptake. Chronic treatment did not impact the progressive reduction in the amplitude of DA responses when, using 20 or 60 Hz pulse trains, the VTA was stimulated every 6 s to deplete DA. Specifically, the amplitude of DA responses to 60 Hz pulse trains was initially reduced compared to control mice, but by the fifth pulse train, there was no longer a treatment effect. However, chronic lithium treatment attenuated d-amphetamine-induced increases in DA responses to 20 Hz pulse trains stimulation. Our data suggest that long-term administration of lithium may ameliorate mania phenotypes by normalizing the readily releasable DA pool in VTA axon terminals in the NAc. Read the Editorial Highlight for this article on Page 520. © 2016 International Society for Neurochemistry.

SPECIAL ISSUE DEVOTED TO THE 25th ANNIVERSARY OF THE A.M. PROKHOROV GENERAL PHYSICS INSTITUTE: High-speed ablation of ultradeep channels by a phase-conjugate dynamically controlled passively Q-switched Nd:YAG laser

NASA Astrophysics Data System (ADS)

Basiev, T. T.; Garnov, S. V.; Klimentov, S. M.; Pivovarov, P. A.; Gavrilov, A. V.; Smetanin, S. N.; Solokhin, S. A.; Fedin, A. V.

2007-10-01

Parameters of high-speed ablation of ultradeep channels by controlled pulse trains from a single-mode phase-conjugate dynamic cavity Nd:YAG laser emitting 20-200-ns, 70-250-mJ pulses at a pulse repetition rate in a train of 40-250 kHz are studied. The optimal parameters of ablation are found, for which a long-lived region of a hot rarefied gas was maintained in the ultradeep channel, which suppressed the shielding action of the surface plasma. The control of the lasing process during ablation optimises not only the heating and plasma formation, but also the removal of the processed material in the pause between laser pulses. Adaptive regulation of lasing parameters during ablation made it possible to obtain ultradeep channels of length 8-27 mm and diameters 80-300 μm of the input and output holes in metals (aluminium, steel and Inconel 718 nickel superalloy) and ultrahard ceramics (Al2O3, AlN, SiC).

Using Ultrasound to Enhance Medical Students' Femoral Vascular Physical Examination Skills.

PubMed

Ahn, Justin S; French, Andrew J; Thiessen, Molly E W; Browne, Vaughn; Deutchman, Mark; Guiton, Gretchen; Madigosky, Wendy; Kendall, John L

2015-10-01

To determine whether the addition of ultrasound to traditional physical examination instruction improves junior medical students' abilities to locate the femoral pulse. Initially, 150 second-year medical students were taught the femoral pulse examination using traditional bedside teaching on standardized patients and online didactic videos. Students were then randomized into 2 groups: group 1 received ultrasound training first and then completed the standardized examination; and group 2 performed the standardized examination first and then received ultrasound training. On the standardized patients, the femoral artery was marked with invisible ink before the sessions using ultrasound. Compared to these markers, students were then evaluated on the accuracy of femoral artery pulse palpation and the estimated location of the femoral vein. All students completed a self-assessment survey after the ultrasound sessions. Ultrasound training improved the students' ability to palpate the femoral pulse (P= .02). However, ultrasound did not facilitate correct estimation of the femoral vein's anatomic location (P = .09). Confidence levels in localizing the femoral artery and vein were equal between groups at baseline, and both increased after the ultrasound sessions. The addition of ultrasound teaching to traditional physical examination instruction enhanced medical student competency and confidence with the femoral vascular examination. However, understanding of anatomy may require emphasis on precourse didactic material, but further study is required. © 2015 by the American Institute of Ultrasound in Medicine.

Pilot study of Iopamidol-based quantitative pH imaging on a clinical 3T MR scanner.

PubMed

Müller-Lutz, Anja; Khalil, Nadia; Schmitt, Benjamin; Jellus, Vladimir; Pentang, Gael; Oeltzschner, Georg; Antoch, Gerald; Lanzman, Rotem S; Wittsack, Hans-Jörg

2014-12-01

The objective of this study was to show the feasibility to perform Iopamidol-based pH imaging via clinical 3T magnetic resonance imaging (MRI) using chemical exchange saturation transfer (CEST) imaging with pulse train presaturation. The pulse train presaturation scheme of a CEST sequence was investigated for Iopamidol-based pH measurements using a 3T magnetic resonance (MR) scanner. The CEST sequence was applied to eight tubes filled with 100-mM Iopamidol solutions with pH values ranging from 5.6 to 7.0. Calibration curves for pH quantification were determined. The dependence of pH values on the concentration of Iopamidol was investigated. An in vivo measurement was performed in one patient who had undergone a previous contrast-enhanced computed tomography (CT) scan with Iopamidol. The pH values of urine measured with CEST MRI and with a pH meter were compared. In the measured pH range, pH imaging using CEST imaging with pulse train presaturation was possible. Dependence between the pH value and the concentration of Iopamidol was not observed. In the in vivo investigation, the pH values in the human bladder measured by the Iopamidol CEST sequence and in urine were consistent. Our study shows the feasibility of using CEST imaging with Iopamidol for quantitative pH mapping in vitro and in vivo on a 3T MR scanner.

Shot noise limited characterization of ultraweak femtosecond pulse trains.

PubMed

Schwartz, Osip; Raz, Oren; Katz, Ori; Dudovich, Nirit; Oron, Dan

2011-01-17

Ultrafast science is inherently, due to the lack of fast enough detectors and electronics, based on nonlinear interactions. Typically, however, nonlinear measurements require significant powers and often operate in a limited spectral range. Here we overcome the difficulties of ultraweak ultrafast measurements by precision time-domain localization of spectral components. We utilize this for linear self-referenced characterization of pulse trains having ∼ 1 photon per pulse, a regime in which nonlinear techniques are impractical, at a temporal resolution of ∼ 10 fs. This technique does not only set a new scale of sensitivity in ultrashort pulse characterization, but is also applicable in any spectral range from the near-infrared to the deep UV.

Experimental realization of spatially separated entanglement with continuous variables using laser pulse trains

PubMed Central

Zhang, Yun; Okubo, Ryuhi; Hirano, Mayumi; Eto, Yujiro; Hirano, Takuya

2015-01-01

Spatially separated entanglement is demonstrated by interfering two high-repetition squeezed pulse trains. The entanglement correlation of the quadrature amplitudes between individual pulses is interrogated. It is characterized in terms of the sufficient inseparability criterion with an optimum result of in the frequency domain and in the time domain. The quantum correlation is also observed when the two measurement stations are separated by a physical distance of 4.5 m, which is sufficiently large to demonstrate the space-like separation, after accounting for the measurement time. PMID:26278478

Tooth pulp stimulation as an unconditioned stimulus in defensive instrumental conditioning.

PubMed

Jastreboff, P J; Keller, O; Zieliński, K

1977-01-01

In an experiment performed on five cats, stable escape and avoidance reflexes in a bar-pressing situation were established using tooth pulp electric stimulation as the unconditioned stimulus. The influence of changes in parameters of the unconditioned stimulus (current intensity, single pulse and train durations, frequency of pulses and rate of train presentations) on unconditioned and instrumental responses was analysed in three additional subjects. Among other relationships the dependence of the threshold of bar press responses on the amount of charge in a single pulse was determined.

Quadro-pulse stimulation is more effective than paired-pulse stimulation for plasticity induction of the human motor cortex.

PubMed

Hamada, Masashi; Hanajima, Ritsuko; Terao, Yasuo; Arai, Noritoshi; Furubayashi, Toshiaki; Inomata-Terada, Satomi; Yugeta, Akihiro; Matsumoto, Hideyuki; Shirota, Yuichiro; Ugawa, Yoshikazu

2007-12-01

Repetitive paired-pulse transcranial magnetic stimulation (TMS) at I-wave periodicity has been shown to induce a motor-evoked potential (MEP) facilitation. We hypothesized that a greater enhancement of motor cortical excitability is provoked by increasing the number of pulses per train beyond those by paired-pulse stimulation (PPS). We explored motor cortical excitability changes induced by repetitive application of trains of four monophasic magnetic pulses (quadro-pulse stimulation: QPS) at 1.5-ms intervals, repeated every 5s over the motor cortex projecting to the hand muscles. The aftereffects of QPS were evaluated with MEPs to a single-pulse TMS, motor threshold (MT), and responses to brain-stem stimulation. These effects were compared to those after PPS. To evaluate the QPS safety, we also studied the spread of excitation and after discharge using surface electromyograms (EMGs) of hand and arm muscles. Sizes of MEPs from the hand muscle were enhanced for longer than 75min after QPS; they reverted to the baseline at 90min. Responses to brain-stem stimulation from the hand muscle and cortical MEPs from the forearm muscle were unchanged after QPS over the hand motor area. MT was unaffected by QPS. No spreads of excitation were detected after QPS. The appearance rate of after discharges during QPS was not different from that during sham stimulation. Results show that QPS can safely induce long-lasting, topographically specific enhancement of motor cortical excitability. QPS is more effective than PPS for inducing motor cortical plasticity.

Method for generating a plasma wave to accelerate electrons

DOEpatents

Umstadter, D.; Esarey, E.; Kim, J.K.

1997-06-10

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

Advanced Orion Optimized Laser System Analysis

NASA Technical Reports Server (NTRS)

1996-01-01

Contractor shall perform a complete analysis of the potential of the solid state laser in the very long pulse mode (100 ns pulse width, 10-30 hz rep-rate) and in the very short pulse mode (100 ps pulse width 10-30 hz rep rate) concentrating on the operation of the device in the 'hot-rod' mode, where no active cooling the laser operation is attempted. Contractor's calculations shall be made of the phase aberrations which develop during the repped-pulse train, and the results shall feed into the adaptive optics analyses. The contractor shall devise solutions to work around ORION track issues. A final report shall be furnished to the MSFC COTR including all calculations and analysis of estimates of bulk phase and intensity aberration distribution in the laser output beam as a function of time during the repped-pulse train for both wave forms (high-energy/long-pulse, as well as low-energy/short-pulse). Recommendations shall be made for mitigating the aberrations by laser re-design and/or changes in operating parameters of optical pump sources and/or designs.

Method for generating a plasma wave to accelerate electrons

DOEpatents

Umstadter, Donald; Esarey, Eric; Kim, Joon K.

1997-01-01

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

Transcranial electric stimulation for intraoperative motor evoked potential monitoring: dependence of required stimulation current on interstimulus interval value.

PubMed

Joksimovic, Boban; Szelenyi, Andrea; Seifert, Volker; Damjanovic, Aleksandar; Damjanovic, Aleksandra; Rasulic, Lukas

2015-05-01

To evaluate the relationship between stimulus intensity by constant current transcranial electric stimulation and interstimulus interval (ISI) for eliciting muscle motor evoked potentials (MEPs) in three different hand muscles and the tibialis anterior muscles. We tested intraoperatively different monophasic constant current pulses and ISIs in 22 patients with clinically normal motor function. Motor thresholds of contralateral muscle MEPs were determined at 0.5 milliseconds (ms) pulse duration and ISIs of 1, 2, 3, 4, 5, and 10 ms using a train of 2, 3, and 5 monophasic constant current pulses of 62 to 104 mA before craniotomy and after closure of the dura mater. The lowest stimulation threshold to elicit MEPs in the examined muscles was achieved with a train of 5 pulses (ISI: 3 ms) before craniotomy, which was statistically significant compared with 2 pulses (ISI: 3 ms) as well as 3 pulses (ISIs: 3 and 10 ms). An ISI of 3 ms gave the lowest motor thresholds with statistical significance compared with the ISIs of 4 ms (2 pulses) and of 1 ms (3 pulses). All current intensity (mA) and ISI (ms) relationship graphs had a trend of the exponential function as y = a + bx + c ρ (x), where y is intensity (mA) and x is ISI (ms). The minimum of the function was determined for each patient and each muscle. The difference was statistically significant between 3 and 5 pulses before craniotomy and between 3 and 5 pulses and 2 and 5 pulses after closure of the dura mater. In adult neurosurgical patients with a normal motor status, a train of 5 pulses and an ISI of 3 ms provide the lowest motor thresholds. We provided evidence of the dependence of required stimulation current on ISI. Georg Thieme Verlag KG Stuttgart · New York.

Laser frequency multiplication

NASA Astrophysics Data System (ADS)

1991-11-01

A high quality mode locked pulse train was obtained at 9.55 microns, the CO2 wavelength chosen for frequency doubling into the atmospheric window at 4.8 microns. The pulse train consists of a 3 micro sec burst of 1.5 nsec pulses separated by 40 nsec, in a TEM (sub 00) mode and with a total energy of 100 mJ. The pulse intensity without focussing is about 3 MW/sq.cm., already quite close to the target intensity of 10 MW/sq.cm. for frequency doubling in a AgGaSe2 crystal. The mode-locked train is obtained by intracavity modulation at 12.5 MHz using a germanium crystal driven with a power of about 30 Watts. Line selection is achieved firstly by the use of a 0.92 mm thick CaF2 plate at the Brewster angle within the cavity, which completely suppresses 10.6 micron band radiation. Secondly, a particular rotational line, the P20 at 9.55 micron, is selected by the injection of a continuous beam is mode-matched to the pulsed laser cavity using a long focal length lens, and for best line-locking it is necessary to fine tune the length of the pulsed laser resonator. Injection causes substantial depression of the gain switched spike.

[Autogenic training as a therapy for adjustment disorder in adults].

PubMed

Jojić, Boris R; Leposavić, Ljubica M

2005-01-01

Autogenic training is a widely recognised psychotherapy technique. The British School of Autogenic Training cites a large list of disorders, states, and changes, where autogenic training may prove to be of help. We wanted to explore the application of autogenic training as a therapy for adjustment disorder in adults. Our sample consisted of a homogeneous group of 35 individuals, with an average age of 39.3 +/- 1.6 years, who were diagnosed with adjustment disorder, F 43.2, in accordance with ICD 10 search criteria. The aim of our study was to research the effectiveness of autogenic training as a therapy for adjustment disorder in adults, by checking the influence of autogenic training on the biophysical and biochemical indicators of adjustment disorder. We measured the indicators of adjustment disorder and their changes in three phases: before the beginning, immediately after the beginning, and six months after the completion, of a practical course in autogenic training. We measured systolic and diastolic arterial blood pressure, brachial pulse rate as well as the levels of cortisol in plasma, of cholesterol in blood, and of glucose. During that period, autogenic training functioned as the sole therapy. The study confirmed our preliminary assumptions. The measurements we performed demonstrated that arterial blood pressure, pulse rate, concentration of cholesterol and cortisol, after the application of autogenic training among the subjects suffering from adjustment disorder, were lower in comparison to the initial values. These values remained lower even six months after the completion of the practical course in autogenic training. Autogenic training significantly decreases the values of physiological indicators of adjustment disorder, diminishes the effects of stress in an individual, and helps adults to cope with stress, facilitating their recuperation.

Characterization of quantum interference control of injected currents in LT-GaAs for carrier-envelope phase measurements.

PubMed

Roos, Peter; Quraishi, Qudsia; Cundiff, Steven; Bhat, Ravi; Sipe, J

2003-08-25

We use two mutually coherent, harmonically related pulse trains to experimentally characterize quantum interference control (QIC) of injected currents in low-temperature-grown gallium arsenide. We observe real-time QIC interference fringes, optimize the QIC signal fidelity, uncover critical signal dependences regarding beam spatial position on the sample, measure signal dependences on the fundamental and second harmonic average optical powers, and demonstrate signal characteristics that depend on the focused beam spot sizes. Following directly from our motivation for this study, we propose an initial experiment to measure and ultimately control the carrier-envelope phase evolution of a single octave-spanning pulse train using the QIC phenomenon.

Dynamic optical arbitrary waveform shaping based on cascaded optical modulators of single FBG.

PubMed

Chen, Jingyuan; Li, Peili

2015-08-10

A dynamic optical arbitrary waveform generation (O-AWG) with amplitude and phase independently controlled in optical modulators of single fiber Bragg Grating (FBG) has been proposed. This novel scheme consists of several optical modulators. In the optical modulator (O-MOD), a uniform FBG is used to filter spectral component of the input signal. The amplitude is controlled by fiber stretcher (FS) in Mach-Zehnder interference (MZI) structure through interference of two MZI arms. The phase is manipulated via the second FS in the optical modulator. This scheme is investigated by simulation. Consequently, optical pulse trains with different waveforms as well as pulse trains with nonuniform pulse intensity, pulse spacing and pulse width within each period are obtained through FSs adjustment to alter the phase shifts of signal in each O-MOD.

Effect of current on the maximum possible reward.

PubMed

Gallistel, C R; Leon, M; Waraczynski, M; Hanau, M S

1991-12-01

Using a 2-lever choice paradigm with concurrent variable interval schedules of reward, it was found that when pulse frequency is increased, the preference-determining rewarding effect of 0.5-s trains of brief cathodal pulses delivered to the medial forebrain bundle of the rat saturates (stops increasing) at values ranging from 200 to 631 pulses/s (pps). Raising the current lowered the saturation frequency, which confirms earlier, more extensive findings showing that the rewarding effect of short trains saturates at pulse frequencies that vary from less than 100 pps to more than 800 pps, depending on the current. It was also found that the maximum possible reward--the magnitude of the reward at or beyond the saturation pulse frequency--increases with increasing current. Thus, increasing the current reduces the saturation frequency but increases the subjective magnitude of the maximum possible reward.

Adjustable repetition-rate multiplication of optical pulses using fractional temporal Talbot effect with preceded binary intensity modulation

NASA Astrophysics Data System (ADS)

Xie, Qijie; Zheng, Bofang; Shu, Chester

2017-05-01

We demonstrate a simple approach for adjustable multiplication of optical pulses in a fiber using the temporal Talbot effect. Binary electrical patterns are used to control the multiplication factor in our approach. The input 10 GHz picosecond pulses are pedestal-free and are shaped directly from a CW laser. The pulses are then intensity modulated by different sets of binary patterns prior to entering a fiber of fixed dispersion. Tunable repetition-rate multiplication by different factors of 2, 4, and 8 have been achieved and up to 80 GHz pulse train has been experimentally generated. We also evaluate numerically the influence of the extinction ratio of the intensity modulator on the performance of the multiplied pulse train. In addition, the impact of the modulator bias on the uniformity of the output pulses has also been analyzed through simulation and experiment and a good agreement is reached. Last, we perform numerical simulation on the RF spectral characteristics of the output pulses. The insensitivity of the signal-to-subharmonic noise ratio (SSNR) to the laser linewidth shows that our multiplication scheme is highly tolerant to the incoherence of the input optical pulses.

A computational model that predicts behavioral sensitivity to intracortical microstimulation

PubMed Central

Kim, Sungshin; Callier, Thierri; Bensmaia, Sliman J.

2016-01-01

Objective Intracortical microstimulation (ICMS) is a powerful tool to investigate the neural mechanisms of perception and can be used to restore sensation for patients who have lost it. While sensitivity to ICMS has previously been characterized, no systematic framework has been developed to summarize the detectability of individual ICMS pulse trains or the discriminability of pairs of pulse trains. Approach We develop a simple simulation that describes the responses of a population of neurons to a train of electrical pulses delivered through a microelectrode. We then perform an ideal observer analysis on the simulated population responses to predict the behavioral performance of non-human primates in ICMS detection and discrimination tasks. Main results Our computational model can predict behavioral performance across a wide range of stimulation conditions with high accuracy (R2 = 0.97) and generalizes to novel ICMS pulse trains that were not used to fit its parameters. Furthermore, the model provides a theoretical basis for the finding that amplitude discrimination based on ICMS violates Weber's law. Significance The model can be used to characterize the sensitivity to ICMS across the range of perceptible and safe stimulation regimes. As such, it will be a useful tool for both neuroscience and neuroprosthetics. PMID:27977419

A computational model that predicts behavioral sensitivity to intracortical microstimulation.

PubMed

Kim, Sungshin; Callier, Thierri; Bensmaia, Sliman J

2017-02-01

Intracortical microstimulation (ICMS) is a powerful tool to investigate the neural mechanisms of perception and can be used to restore sensation for patients who have lost it. While sensitivity to ICMS has previously been characterized, no systematic framework has been developed to summarize the detectability of individual ICMS pulse trains or the discriminability of pairs of pulse trains. We develop a simple simulation that describes the responses of a population of neurons to a train of electrical pulses delivered through a microelectrode. We then perform an ideal observer analysis on the simulated population responses to predict the behavioral performance of non-human primates in ICMS detection and discrimination tasks. Our computational model can predict behavioral performance across a wide range of stimulation conditions with high accuracy (R 2  = 0.97) and generalizes to novel ICMS pulse trains that were not used to fit its parameters. Furthermore, the model provides a theoretical basis for the finding that amplitude discrimination based on ICMS violates Weber's law. The model can be used to characterize the sensitivity to ICMS across the range of perceptible and safe stimulation regimes. As such, it will be a useful tool for both neuroscience and neuroprosthetics.

A computational model that predicts behavioral sensitivity to intracortical microstimulation

NASA Astrophysics Data System (ADS)

Kim, Sungshin; Callier, Thierri; Bensmaia, Sliman J.

2017-02-01

Objective. Intracortical microstimulation (ICMS) is a powerful tool to investigate the neural mechanisms of perception and can be used to restore sensation for patients who have lost it. While sensitivity to ICMS has previously been characterized, no systematic framework has been developed to summarize the detectability of individual ICMS pulse trains or the discriminability of pairs of pulse trains. Approach. We develop a simple simulation that describes the responses of a population of neurons to a train of electrical pulses delivered through a microelectrode. We then perform an ideal observer analysis on the simulated population responses to predict the behavioral performance of non-human primates in ICMS detection and discrimination tasks. Main results. Our computational model can predict behavioral performance across a wide range of stimulation conditions with high accuracy (R 2 = 0.97) and generalizes to novel ICMS pulse trains that were not used to fit its parameters. Furthermore, the model provides a theoretical basis for the finding that amplitude discrimination based on ICMS violates Weber’s law. Significance. The model can be used to characterize the sensitivity to ICMS across the range of perceptible and safe stimulation regimes. As such, it will be a useful tool for both neuroscience and neuroprosthetics.

Time dynamics of burst-train filamentation assisted femtosecond laser machining in glasses.

PubMed

Esser, Dagmar; Rezaei, Saeid; Li, Jianzhao; Herman, Peter R; Gottmann, Jens

2011-12-05

Bursts of femtosecond laser pulses with a repetition rate of f = 38.5MHz were created using a purpose-built optical resonator. Single Ti:Sapphire laser pulses, trapped inside a resonator and released into controllable burst profiles by computer generated trigger delays to a fast Pockels cell switch, drove filamentation-assisted laser machining of high aspect ratio holes deep into transparent glasses. The time dynamics of the hole formation and ablation plume physics on 2-ns to 400-ms time scales were examined in time-resolved side-view images recorded with an intensified-CCD camera during the laser machining process. Transient effects of photoluminescence and ablation plume emissions confirm the build-up of heat accumulation effects during the burst train, the formation of laser-generated filaments and plume-shielding effects inside the deeply etched vias. The small time interval between the pulses in the present burst train enabled a more gentle modification in the laser interaction volume that mitigated shock-induced microcracks compared with single pulses.

Plasma dynamics near critical density inferred from direct measurements of laser hole boring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Chao; Tochitsky, Sergei Ya.; Fiuza, Frederico

Here, we use multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of CO 2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulsemore » train. We present a heuristic theory that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. Furthermore, the measured values of v HB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.« less

Plasma dynamics near critical density inferred from direct measurements of laser hole boring

DOE PAGES

Gong, Chao; Tochitsky, Sergei Ya.; Fiuza, Frederico; ...

2017-06-24

Here, we use multiframe picosecond optical interferometry to make direct measurements of the hole boring velocity, vHB, of the density cavity pushed forward by a train of CO 2 laser pulses in a near critical density helium plasma. As the pulse train intensity rises, the increasing radiation pressure of each pulse pushes the density cavity forward and the plasma electrons are strongly heated. After the peak laser intensity, the plasma pressure exerted by the heated electrons strongly impedes the hole boring process and the vHB falls rapidly as the laser pulse intensity falls at the back of the laser pulsemore » train. We present a heuristic theory that allows the estimation of the plasma electron temperature from the measurements of the hole boring velocity. Furthermore, the measured values of v HB, and the estimated values of the heated electron temperature as a function of laser intensity are in reasonable agreement with those obtained from two-dimensional numerical simulations.« less

Sub-10-fs control of dissociation pathways in the hydrogen molecular ion with a few-pulse attosecond pulse train

NASA Astrophysics Data System (ADS)

Nabekawa, Yasuo; Furukawa, Yusuke; Okino, Tomoya; Amani Eilanlou, A.; Takahashi, Eiji J.; Yamanouchi, Kaoru; Midorikawa, Katsumi

2016-09-01

The control of the electronic states of a hydrogen molecular ion by photoexcitation is considerably difficult because it requires multiple sub-10 fs light pulses in the extreme ultraviolet (XUV) wavelength region with a sufficiently high intensity. Here, we demonstrate the control of the dissociation pathway originating from the 2pσu electronic state against that originating from the 2pπu electronic state in a hydrogen molecular ion by using a pair of attosecond pulse trains in the XUV wavelength region with a train-envelope duration of ~4 fs. The switching time from the peak to the valley in the oscillation caused by the vibrational wavepacket motion in the 1sσg ground electronic state is only 8 fs. This result can be classified as the fastest control, to the best of our knowledge, of a molecular reaction in the simplest molecule on the basis of the XUV-pump and XUV-probe scheme.

Propagation failures, breathing pulses, and backfiring in an excitable reaction-diffusion system.

PubMed

Manz, Niklas; Steinbock, Oliver

2006-09-01

We report results from experiments with a pseudo-one-dimensional Belousov-Zhabotinsky reaction that employs 1,4-cyclohexanedione as its organic substrate. This excitable system shows traveling oxidation pulses and pulse trains that can undergo complex sequences of propagation failures. Moreover, we present examples for (i) breathing pulses that undergo periodic changes in speed and size and (ii) backfiring pulses that near their back repeatedly generate new pulses propagating in opposite direction.

Effect of Pulse Polarity on Thresholds and on Non-monotonic Loudness Growth in Cochlear Implant Users.

PubMed

Macherey, Olivier; Carlyon, Robert P; Chatron, Jacques; Roman, Stéphane

2017-06-01

Most cochlear implants (CIs) activate their electrodes non-simultaneously in order to eliminate electrical field interactions. However, the membrane of auditory nerve fibers needs time to return to its resting state, causing the probability of firing to a pulse to be affected by previous pulses. Here, we provide new evidence on the effect of pulse polarity and current level on these interactions. In experiment 1, detection thresholds and most comfortable levels (MCLs) were measured in CI users for 100-Hz pulse trains consisting of two consecutive biphasic pulses of the same or of opposite polarity. All combinations of polarities were studied: anodic-cathodic-anodic-cathodic (ACAC), CACA, ACCA, and CAAC. Thresholds were lower when the adjacent phases of the two pulses had the same polarity (ACCA and CAAC) than when they were different (ACAC and CACA). Some subjects showed a lower threshold for ACCA than for CAAC while others showed the opposite trend demonstrating that polarity sensitivity at threshold is genuine and subject- or electrode-dependent. In contrast, anodic (CAAC) pulses always showed a lower MCL than cathodic (ACCA) pulses, confirming previous reports. In experiments 2 and 3, the subjects compared the loudness of several pulse trains differing in current level separately for ACCA and CAAC. For 40 % of the electrodes tested, loudness grew non-monotonically as a function of current level for ACCA but never for CAAC. This finding may relate to a conduction block of the action potentials along the fibers induced by a strong hyperpolarization of their central processes. Further analysis showed that the electrodes showing a lower threshold for ACCA than for CAAC were more likely to yield a non-monotonic loudness growth. It is proposed that polarity sensitivity at threshold reflects the local neural health and that anodic asymmetric pulses should preferably be used to convey sound information while avoiding abnormal loudness percepts.

3D Ta/TaO x /TiO2/Ti synaptic array and linearity tuning of weight update for hardware neural network applications

NASA Astrophysics Data System (ADS)

Wang, I.-Ting; Chang, Chih-Cheng; Chiu, Li-Wen; Chou, Teyuh; Hou, Tuo-Hung

2016-09-01

The implementation of highly anticipated hardware neural networks (HNNs) hinges largely on the successful development of a low-power, high-density, and reliable analog electronic synaptic array. In this study, we demonstrate a two-layer Ta/TaO x /TiO2/Ti cross-point synaptic array that emulates the high-density three-dimensional network architecture of human brains. Excellent uniformity and reproducibility among intralayer and interlayer cells were realized. Moreover, at least 50 analog synaptic weight states could be precisely controlled with minimal drifting during a cycling endurance test of 5000 training pulses at an operating voltage of 3 V. We also propose a new state-independent bipolar-pulse-training scheme to improve the linearity of weight updates. The improved linearity considerably enhances the fault tolerance of HNNs, thus improving the training accuracy.

Determination of Anaerobic Threshold by Monitoring the O2 Pulse Changes in Endurance Cyclists.

PubMed

Nikooie, Rohollah

2016-06-01

The purpose of this study was to determine the validity of anaerobic threshold (AnT)-equivalent to the second turn point for lactate (LTP2)-estimation using the O2 pulse changes in highly trained endurance cyclists who do not show heart rate deflection point (HRDP) during incremental testing. Sixteen endurance cyclists (age, 24.8 ± 4.7 years) and fifteen active men (age, 24.8 ± 3.7 years) performed an incremental cycling test to exhaustion. Pulmonary oxygen uptake (V[Combining Dot Above]O2) and other hemodynamic variables, heart rate, and blood lactate concentration were measured continuously throughout the test. O2 pulse anaerobic threshold (O2 pulse-AnT) was defined as the second turn point in O2 pulse-workload curve. LTP2 was considered as gold standard assessment of AnT and was applied to confirm the validity of O2 pulse-AnT. Intraclass correlation coefficients and the Bland-Altman method were used to determine the relationship and agreement between the O2 corresponding to LTP2 and O2 pulse-AnT, respectively. The active men and 68.7% of the endurance cyclists showed HRDP, whereas all subjects showed O2 pulse-AnT during incremental testing. In both groups, the values for V[Combining Dot Above]O2 corresponding to LTP2 were not significantly different from the V[Combining Dot Above]O2 at O2 pulse-AnT. The V[Combining Dot Above]O2 at LTP2 and O2 pulse-AnT were highly correlated (endurance cyclists: R = 0.68; standard error of estimate [SEE] = 3.74 ml·kg·min and active men: R = 0.58; SEE = 2.91 ml·kg·min) and Bland-Altman plot revealed the limit of agreement of O2 at LTP2 and O2 pulse-AnT differences between 5.1 and 8.6 ml·kg·min (95% CI). In summary, results of this study showed that the second turn point in the O2 pulse-workload curve occurs around LTP2. Therefore, using O2 pulse-AnT is recommended for the noninvasive determination of AnT in highly trained endurance cyclists who do not show HRDP during incremental exercise.

Aerobic Exercise Training and Arterial Changes in African Americans versus Caucasians.

PubMed

Ranadive, Sushant M; Yan, Huimin; Lane, Abbi D; Kappus, Rebecca M; Cook, Marc D; Sun, Peng; Harvey, Idethia; Ploutz-Synder, Robert; Woods, Jeffrey A; Wilund, Kenneth R; Fernhall, B O

2016-01-01

African Americans (AA) have increased carotid artery intima-media thickness and decreased vascular function compared with their Caucasian (CA) peers. Aerobic exercise prevents and potentially reverses arterial dysfunction. The purpose of this study was to examine the effect of 8 wk of moderate- to high-intensity aerobic training in young healthy sedentary AA and CA men and women. Sixty-four healthy volunteers (men, 28; women, 36) with mean age 24 yr underwent measures of arterial structure, function, and blood pressure (BP) variables at baseline, after the 4-wk control period, and 8 wk after training. There was a significant increase in VO2peak among both groups after exercise training. Brachial systolic BP decreased significantly after the control period in both groups but not after exercise training. Carotid pulse pressure decreased significantly in both groups after exercise training as compared with that in baseline. There was no change in any of the other BP variables. AA had higher intima-media thickness at baseline and after the control period but it significantly decreased after exercise training compared with that of CA. AA had significantly lower baseline forearm blood flow and reactive hyperemia compared with those of CA, but exercise training had no effect on these variables. There was no significant difference in arterial stiffness (central pulse wave velocity) and wave-reflection (augmentation index) between the two groups at any time point. This is the first study to show that 8 wk of aerobic exercise training causes significant improvement in the arterial structure in young, healthy AA, making it comparable with the CA and with minimal effects on BP variables.

Patterning and reduction of graphene oxide using femtosecond-laser irradiation

NASA Astrophysics Data System (ADS)

Kang, SeungYeon; Evans, Christopher C.; Shukla, Shobha; Reshef, Orad; Mazur, Eric

2018-07-01

Graphene has emerged as one of the most versatile materials ever discovered due to its extraordinary electronic, optical, thermal, and mechanical properties. However, device fabrication is a well-known challenge and requires novel fabrication methods to realize the complex integration of graphene-based devices. Here, we demonstrate direct laser writing of reduced graphene oxide using femtosecond-laser irradiation at λ = 795 nm. We perform a systematic study of the reduction process of graphene oxide to graphene by varying both the laser fluence and the pulse repetition rate. Our observations show that the reduction has both thermal and non-thermal features, and suggest that we can achieve better resolution and conductivity using kHz pulse trains than using MHz pulse trains or a continuous wave laser. Our reduced graphene oxide lines written at 10-kHz exhibit a 5 order-of-magnitude decrease in resistivity compared to a non-irradiated control sample. This study provides new insight into the reduction process of graphene oxide and opens doors to achieving a high degree of flexibility and control in the fabrication of graphene layers.

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

DOE PAGES

Faatz, B.; Plönjes, E.; Ackermann, S.; ...

2016-06-20

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated inmore » both FELs simultaneously. Here, FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.« less

Neural-network-designed pulse sequences for robust control of singlet-triplet qubits

NASA Astrophysics Data System (ADS)

Yang, Xu-Chen; Yung, Man-Hong; Wang, Xin

2018-04-01

Composite pulses are essential for universal manipulation of singlet-triplet spin qubits. In the absence of noise, they are required to perform arbitrary single-qubit operations due to the special control constraint of a singlet-triplet qubit, while in a noisy environment, more complicated sequences have been developed to dynamically correct the error. Tailoring these sequences typically requires numerically solving a set of nonlinear equations. Here we demonstrate that these pulse sequences can be generated by a well-trained, double-layer neural network. For sequences designed for the noise-free case, the trained neural network is capable of producing almost exactly the same pulses known in the literature. For more complicated noise-correcting sequences, the neural network produces pulses with slightly different line shapes, but the robustness against noises remains comparable. These results indicate that the neural network can be a judicious and powerful alternative to existing techniques in developing pulse sequences for universal fault-tolerant quantum computation.

Design of a Low-Energy FARAD Thruster

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Rose, M. F.; Miller, R.; Best, S.; Owens, T.; Dankanich, J.

2007-01-01

The design of an electrodeless thruster that relies on a pulsed, rf-assisted discharge and electromagnetic acceleration using an inductive coil is presented. The thruster design is optimized using known performance,scaling parameters, and experimentally-determined design rules, with design targets for discharge energy, plasma exhaust velocity; and thrust efficiency of 100 J/pulse, 25 km/s, and 50%, respectively. Propellant is injected using a high-speed gas valve and preionized by a pulsed-RF signal supplied by a vector inversion generator, allowing for current sheet formation at lower discharge voltages and energies relative to pulsed inductive accelerators that do not employ preionization. The acceleration coil is designed to possess an inductance of at least 700 nH while the target stray (non-coil) inductance in the circuit is 70 nH. A Bernardes and Merryman pulsed power train or a pulse compression power train provide current to the acceleration coil and solid-state components are used to switch both powertrains.

An experimental vestibular neural prosthesis: design and preliminary results with rhesus monkeys stimulated with modulated pulses.

PubMed

Nie, Kaibao; Ling, Leo; Bierer, Steven M; Kaneko, Chris R S; Fuchs, Albert F; Oxford, Trey; Rubinstein, Jay T; Phillips, James O

2013-06-01

A vestibular neural prosthesis was designed on the basis of a cochlear implant for treatment of Meniere's disease and other vestibular disorders. Computer control software was developed to generate patterned pulse stimuli for exploring optimal parameters to activate the vestibular nerve. Two rhesus monkeys were implanted with the prototype vestibular prosthesis and they were behaviorally evaluated post implantation surgery. Horizontal and vertical eye movement responses to patterned electrical pulse stimulations were collected on both monkeys. Pulse amplitude modulated (PAM) and pulse rate modulated (PRM) trains were applied to the lateral canal of each implanted animal. Robust slow-phase nystagmus responses following the PAM or PRM modulation pattern were observed in both implanted monkeys in the direction consistent with the activation of the implanted canal. Both PAM and PRM pulse trains can elicit a significant amount of in-phase modulated eye velocity changes and they could potentially be used for efficiently coding head rotational signals in future vestibular neural prostheses.

Cardiovascular responses to railway noise during sleep in young and middle-aged adults.

PubMed

Tassi, Patricia; Saremi, Mahnaz; Schimchowitsch, Sarah; Eschenlauer, Arnaud; Rohmer, Odile; Muzet, Alain

2010-03-01

The aim of this study was to investigate the effects of nocturnal railway noise on cardiovascular reactivity in young (25.8 +/- 2.6 years) and middle-aged (52.2 +/- 2.5 years) adults during sleep. Thirty-eight subjects slept three nights in the laboratory at 1-week interval. They were exposed to 48 randomized pass-bys of Freight, Passenger and Automotive trains either at an 8-h equivalent sound level of 40 dBA (Moderate) and 50 dBA (High) or at a silent Control night. Heart rate response (HRR), heart response amplitude (HRA), heart response latency (HRL) and finger pulse response (FPR), finger pulse amplitude (FPA) and finger pulse latency (FPL) were recorded to measure cardiovascular reactivity after each noise onset and for time-matched pseudo-noises in the control condition. Results show that Freight trains produced the highest cardiac response (increased HRR, HRA and HRL) compared to Passenger and Automotive. But the vascular response was similar whatever the type of train. Juniors exhibited an increased HRR and HRA as compared to seniors, but there was no age difference on vasoconstriction, except a shorter FPL in seniors. Noise level produced dose-dependent effects on all the cardiovascular indices. Sleep stage at noise occurrence was ineffective for cardiac response, but FPA was reduced when noise occurred during REM sleep. In conclusion, our study is in favor of an important impact of nocturnal railway noise on the cardiovascular system of sleeping subjects. In the limit of the samples studied, Freight trains are the most harmful, probably more because of their special length (duration) than because of their speed (rise time).

Phase incremented echo train acquisition applied to magnetic resonance pore imaging

NASA Astrophysics Data System (ADS)

Hertel, S. A.; Galvosas, P.

2017-02-01

Efficient phase cycling schemes remain a challenge for NMR techniques if the pulse sequences involve a large number of rf-pulses. Especially complex is the Carr Purcell Meiboom Gill (CPMG) pulse sequence where the number of rf-pulses can range from hundreds to several thousands. Our recent implementation of Magnetic Resonance Pore Imaging (MRPI) is based on a CPMG rf-pulse sequence in order to refocus the effect of internal gradients inherent in porous media. While the spin dynamics for spin- 1 / 2 systems in CPMG like experiments are well understood it is still not straight forward to separate the desired pathway from the spectrum of unwanted coherence pathways. In this contribution we apply Phase Incremented Echo Train Acquisition (PIETA) to MRPI. We show how PIETA offers a convenient way to implement a working phase cycling scheme and how it allows one to gain deeper insights into the amplitudes of undesired pathways.

Broadband noise limit in the photodetection of ultralow jitter optical pulses.

PubMed

Sun, Wenlu; Quinlan, Franklyn; Fortier, Tara M; Deschenes, Jean-Daniel; Fu, Yang; Diddams, Scott A; Campbell, Joe C

2014-11-14

Applications with optical atomic clocks and precision timing often require the transfer of optical frequency references to the electrical domain with extremely high fidelity. Here we examine the impact of photocarrier scattering and distributed absorption on the photocurrent noise of high-speed photodiodes when detecting ultralow jitter optical pulses. Despite its small contribution to the total photocurrent, this excess noise can determine the phase noise and timing jitter of microwave signals generated by detecting ultrashort optical pulses. A Monte Carlo simulation of the photodetection process is used to quantitatively estimate the excess noise. Simulated phase noise on the 10 GHz harmonic of a photodetected pulse train shows good agreement with previous experimental data, leading to the conclusion that the lowest phase noise photonically generated microwave signals are limited by photocarrier scattering well above the quantum limit of the optical pulse train.

Method and system for laser-based formation of micro-shapes in surfaces of optical elements

DOEpatents

Bass, Isaac Louis; Guss, Gabriel Mark

2013-03-05

A method of forming a surface feature extending into a sample includes providing a laser operable to emit an output beam and modulating the output beam to form a pulse train having a plurality of pulses. The method also includes a) directing the pulse train along an optical path intersecting an exposed portion of the sample at a position i and b) focusing a first portion of the plurality of pulses to impinge on the sample at the position i. Each of the plurality of pulses is characterized by a spot size at the sample. The method further includes c) ablating at least a portion of the sample at the position i to form a portion of the surface feature and d) incrementing counter i. The method includes e) repeating steps a) through d) to form the surface feature. The sample is free of a rim surrounding the surface feature.

910-m propagation of THz ps pulses through the Atmosphere.

PubMed

Kim, Gyeong-Ryul; Jeon, Tae-In; Grischkowsky, D

2017-10-16

We measured the atmospheric propagation of ps THz pulses with a 0.4-THz bandwidth through a 910-m distance; the pulse delay corresponded to 255 pulses down the pulse train of the mode-locked ring laser excitation pulses. The complexity of the atmosphere requires the use of the complete theory of Essen and Froome to compare the measured time shifts due to both the dry atmosphere and water vapor with theoretical calculations. A new procedure involving the measurement of phase in the frequency domain is introduced and achieves comparable results for the calculated time shifts, compared to the previous direct measurements of time shifts. When the THz pulses were sequentially measured for a distance of 186 and 910 m at the same weather condition, the time variation due to atmospheric turbulence between the two pulses of the 910 m measurement was up to 4 times larger than that between the two pulses of the 186 m measurement. THz long path WVD studies are necessary to evaluate proposed applications in the atmosphere, such as communications and monitoring pollutants and dangerous gases.

910-m propagation of THz ps pulses through the Atmosphere

NASA Astrophysics Data System (ADS)

Kim, Gyeong-Ryul; Jeon, Tae-In; Grischkowsky, D.

2017-10-01

We measured the atmospheric propagation of ps THz pulses with a 0.4-THz bandwidth through a 910-m distance; the pulse delay corresponded to 255 pulses down the pulse train of the mode-locked ring laser excitation pulses. The complexity of the atmosphere requires the use of the complete theory of Essen and Froome to compare the measured time shifts due to both the dry atmosphere and water vapor with theoretical calculations. A new procedure involving the measurement of phase in the frequency domain is introduced and achieves comparable results for the calculated time shifts, compared to the previous direct measurements of time shifts. When the THz pulses were sequentially measured for a distance of 186 and 910 m at the same weather condition, the time variation due to atmospheric turbulence between the two pulses of the 910 m measurement was up to 4 times larger than that between the two pulses of the 186 m measurement. THz long path WVD studies are necessary to evaluate proposed applications in the atmosphere, such as communications and monitoring pollutants and dangerous gases.

Respiratory and Pulse Changes Due to Vestibular Stimulations in a Motion-Based Simulator.

PubMed

Ilbasmis, Savas; Yildiz, Safak

2017-01-01

One of the mechanisms leading to spatial disorientation (SD) is overstimulation of the vestibular system by various aircraft maneuvers. The objective of this study was to observe respiratory rate and pulse changes during vestibular system stimulations with the help of two selected SD training profiles. The respiration and pulse rates of 15 subjects were recorded in response to 2 sequential SD training profiles on a motion-based simulator. The session started with a motionless instruction period (IP), continued with a Coriolis profile (CP) which stimulated the semicircular canals, and ended with a Dark Takeoff profile (DP) which stimulated the otolith organs. Recorded parameter means during profiles were statistically compared with IP mean values. The average age of all subjects was 23.67 ± 1.11. Mean CP respiratory rate (23.43 ± 3.21) was higher than mean IP respiratory rate (21.39 ± 4.27) and mean DP pulse rate (79.88 ± 10.39) was lower than mean IP pulse rate (84.76 ± 14.26) of the subjects. These differences were statistically significant. Data indicate that stimulation of the semicircular canals increased respiration rate while stimulation of the otoliths caused a reduction in pulse rate. This was considered to be a result of vestibulorespiratory reflex. Inputs from the vestibular otolith organs contribute to the control of blood pressure during movement and changes in posture. Predicting pulse and respiratory changes due to aerial maneuvers may be important for pilot safety during flight.Ilbasmis S, Yildiz S. Respiratory and pulse changes due to vestibular stimulations in a motion-based simulator. Aerosp Med Hum Perform. 2017; 88(1):48-51.

Development of a femtosecond micromachining workstation by use of spectral interferometry.

PubMed

Bera, Sudipta; Sabbah, A J; Durfee, Charles G; Squier, Jeff A

2005-02-15

A workstation that permits real-time measurement of ablation depth while micromachining with femtosecond laser pulses is demonstrated. This method incorporates the unamplified pulse train that is available in a chirped-pulse amplification system as the probe in an arrangement that uses spectral interferometry to measure the ablation depth while cutting with the amplified pulse in thin metal films.

Isolated Attosecond Pulse Generation without the Need to Stabilize the Carrier-Envelope Phase of Driving Lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbertson, Steve; Khan, Sabih D.; Wu Yi

2010-08-27

Single isolated attosecond pulses can be extracted from a pulse train with an ultrafast gate in the generation target. By setting the gate width sufficiently narrow with the generalized double optical gating, we demonstrate that single isolated attosecond pulses can be generated with any arbitrary carrier-envelope phase value of the driving laser. The carrier-envelope phase only affects the photon flux, not the pulse duration or contrast. Our results show that isolated attosecond pulses can be generated using carrier-envelope phase unstabilized 23 fs pulses directly from chirped pulse amplifiers.

Full-field wrist pulse signal acquisition and analysis by 3D Digital Image Correlation

NASA Astrophysics Data System (ADS)

Xue, Yuan; Su, Yong; Zhang, Chi; Xu, Xiaohai; Gao, Zeren; Wu, Shangquan; Zhang, Qingchuan; Wu, Xiaoping

2017-11-01

Pulse diagnosis is an essential part in four basic diagnostic methods (inspection, listening, inquiring and palpation) in traditional Chinese medicine, which depends on longtime training and rich experience, so computerized pulse acquisition has been proposed and studied to ensure the objectivity. To imitate the process that doctors using three fingertips with different pressures to feel fluctuations in certain areas containing three acupoints, we established a five dimensional pulse signal acquisition system adopting a non-contacting optical metrology method, 3D digital image correlation, to record the full-field displacements of skin fluctuations under different pressures. The system realizes real-time full-field vibration mode observation with 10 FPS. The maximum sample frequency is 472 Hz for detailed post-processing. After acquisition, the signals are analyzed according to the amplitude, pressure, and pulse wave velocity. The proposed system provides a novel optical approach for digitalizing pulse diagnosis and massive pulse signal data acquisition for various types of patients.

Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

NASA Astrophysics Data System (ADS)

Priebe, Katharina E.; Rathje, Christopher; Yalunin, Sergey V.; Hohage, Thorsten; Feist, Armin; Schäfer, Sascha; Ropers, Claus

2017-12-01

Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—`SQUIRRELS'—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime.

Transverse Mode Dynamics of VCSELs Undergoing Current Modulation

NASA Technical Reports Server (NTRS)

Goorjian, Peter M.; Ning, C. Z.; Agrawal, Govind

2000-01-01

Transverse mode dynamics of a 20-micron-diameter vertical-cavity surface-emitting laser (VCSEL) undergoing gain switching by deep current modulation is studied numerically. The direct current (dc) level is set slightly below threshold and is modulated by a large alternating current (ac). The resulting optical pulse train and transverse-mode patterns are obtained numerically. The ac frequency is varied from 2.5 GHz to 10 GHz, and the ac amplitude is varied from one-half to four times that of the dc level. At high modulation frequencies, a regular pulse train is not generated unless the ac amplitude is large enough. At all modulation frequencies, the transverse spatial profile switches from single-mode to multiple-mode pattern as the ac pumping level is increased. Optical pulse widths vary in the range 5-30 ps. with the pulse width decreasing when either the frequency is increased or the ac amplitude is decreased. The numerical modeling uses an approximation form of the semiconductor Maxwell-Bloch equations. Temporal evolution of the spatial profiles of the laser (and of carrier density) is determined without any assumptions about the type or number of modes. Keywords: VCSELs, current modulation, gain switching, transverse mode dynamics, computational modeling

Frequency-Modulated Orocutaneous Stimulation Promotes Non-nutritive Suck Development in Preterm Infants with Respiratory Distress Syndrome or Chronic Lung Disease

PubMed Central

Barlow, Steven M; Lee, Jaehoon; Wang, Jingyan; Oder, Austin; Hall, Sue; Knox, Kendi; Weatherstone, Kathleen; Thompson, Diane

2013-01-01

Background For the premature infant, extrauterine life is a pathological condition which greatly amplifies the challenges to the brain in establishing functional oromotor behaviors. The extent to which suck can be entrained using a synthetically patterned orocutaneous input to promote its development in preterm infants who manifest chronic lung disease is unknown. Objective To evaluate the effects of a frequency-modulated orocutaneous pulse train delivered through a pneumatically-charged pacifier capable of enhancing non-nutritive suck (NNS) activity in tube-fed premature infants. Methods A randomized trial to evaluate the efficacy of pneumatic orocutaneous stimulation 3x/day on NNS development and length of stay (LOS) in the NICU among 160 newborn infants distributed among 3 subpopulations, including healthy preterm infants (HI), respiratory distress syndrome (RDS), and chronic lung disease (CLD). Study infants received a regimen of orocutaneous pulse trains through a PULSED pressurized silicone pacifier or a SHAM control (blind pacifier) during gavage feeds for up to 10 days. Results Mixed modeling, adjusted for the infant’s gender, gestational age, postmenstrual age, and birth weight, was used to handle interdependency among repeated measures within subjects. A significant main effect for stimulation mode (SHAM pacifier vs PULSED orosensory) was found among preterm infants for NNS Bursts/minute (p=.003), NNS events/minute (p=.033), and for Total Oral Compressions/minute [NNS+nonNNS] (p=.016). Pairwise comparison of adjusted means using Bonferroni adjustment indicated RDS and CLD infants showed the most significant gains on these NNS performance indices. CLD infants in the treatment group showed significantly shorter LOS by an average of 2.5 days. Conclusion Frequency-modulated PULSED orocutaneous pulse train stimuli delivered through a silicone pacifier are effective in facilitating NNS burst development in tube-fed RDS and CLD preterm infants, with an added benefit of reduced LOS for CLD infants. PMID:24310444

Method to generate a pulse train of few-cycle coherent radiation

DOE PAGES

Garcia, Bryant; Hemsing, Erik; Raubenheimer, Tor; ...

2016-09-06

We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. Here, we discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. Wemore » examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.« less

Adaptation of the cortical somatosensory evoked potential following pulsed pneumatic stimulation of the lower face in adults.

PubMed

Custead, Rebecca; Oh, Hyuntaek; Rosner, Austin Oder; Barlow, Steven

2015-10-05

Cortical adaptation to sustained sensory input is a pervasive form of short-term plasticity in neurological systems. Its role in sensory perception in health and disease, or predicting long-term plastic changes resulting from sensory training offers insight into the mechanisms of somatosensory and sensorimotor processing. A 4-channel electroencephalography (EEG) recording montage was placed bilaterally (C3-P3, C4-P4, F7-P3, F8-P4) to characterize the short-term effects of pulsed pneumatic orofacial stimulation on the cortical somatosensory evoked potential (cSEP) in twenty neurotypical adults (mean age=21±2.88 years). A servo-controlled pneumatic amplifier was used to deliver a repetitive series of pneumatic pulse trains (six 50-ms pulses, 5-second intertrain interval) through a linked pair of custom acetal homopolymer probes (aka TAC-Cells) adhered to the nonglabrous skin of the lower face proximal to the right oral angle to synchronously activate mechanoreceptive afferents in the trigeminal nerve. Blocks of pulse trains were counterbalanced among participants and delivered at two rates, 2 and 4Hz. TAC-Cell stimulation of the lower face consistently evoked a series of cSEPs at P7, N20, P28, N38, P75, N85, and P115. The spatial organization and adaptation of the evoked cSEP was dependent on stimulus pulse index (1-6 within the pulse train, p=.012), frequency of stimulus presentation (2 vs 4Hz, p<.001), component (P7-P115, p<.001), and recording montage (channels 1-4, p<.001). Early component latencies (P7-N20) were highly stable in polarity (sign) and latency, and consistent with putative far-field generators (e.g., trigeminal brainstem, ventroposteromedial thalamus). Copyright © 2015 Elsevier B.V. All rights reserved.

Predicting dynamic range and intensity discrimination for electrical pulse-train stimuli using a stochastic auditory nerve model: the effects of stimulus noise.

PubMed

Xu, Yifang; Collins, Leslie M

2005-06-01

This work investigates dynamic range and intensity discrimination for electrical pulse-train stimuli that are modulated by noise using a stochastic auditory nerve model. Based on a hypothesized monotonic relationship between loudness and the number of spikes elicited by a stimulus, theoretical prediction of the uncomfortable level has previously been determined by comparing spike counts to a fixed threshold, Nucl. However, no specific rule for determining Nucl has been suggested. Our work determines the uncomfortable level based on the excitation pattern of the neural response in a normal ear. The number of fibers corresponding to the portion of the basilar membrane driven by a stimulus at an uncomfortable level in a normal ear is related to Nucl at an uncomfortable level of the electrical stimulus. Intensity discrimination limens are predicted using signal detection theory via the probability mass function of the neural response and via experimental simulations. The results show that the uncomfortable level for pulse-train stimuli increases slightly as noise level increases. Combining this with our previous threshold predictions, we hypothesize that the dynamic range for noise-modulated pulse-train stimuli should increase with additive noise. However, since our predictions indicate that intensity discrimination under noise degrades, overall intensity coding performance may not improve significantly.

Background-free millimeter-wave ultra-wideband signal generation based on a dual-parallel Mach-Zehnder modulator.

PubMed

Zhang, Fangzheng; Pan, Shilong

2013-11-04

A novel scheme for photonic generation of a millimeter-wave ultra-wideband (MMW-UWB) signal is proposed and experimentally demonstrated based on a dual-parallel Mach-Zehnder modulator (DPMZM). In the proposed scheme, a single-frequency radio frequency (RF) signal is applied to one sub-MZM of the DPMZM to achieve optical suppressed-carrier modulation, and an electrical control pulse train is applied to the other sub-MZM biased at the minimum transmission point, to get an on/off switchable optical carrier. By filtering out the optical carrier with one of the first-order sidebands, and properly setting the amplitude of the control pulse, an MMW-UWB pulse train without the residual local oscillation is generated after photo-detection. The generated MMW-UWB signal is background-free, because the low-frequency components in the electrical spectrum are effectively suppressed. In the experiment, an MMW-UWB pulse train centered at 25 GHz with a 10-dB bandwidth of 5.5 GHz is successfully generated. The low frequency components are suppressed by 22 dB.

High Frequency, High Gradient Dielectric Wakefield Acceleration Experiments at SLAC and BNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenzweig, James; /UCLA; Travish, Gil

Given the recent success of >GV/m dielectric wakefield accelerator (DWA) breakdown experiments at SLAC, and follow-on coherent Cerenkov radiation production at the UCLA Neptune, a UCLA-USC-SLAC collaboration is now implementing a new set of experiments that explore various DWA scenarios. These experiments are motivated by the opportunities presented by the approval of FACET facility at SLAC, as well as unique pulse-train wakefield drivers at BNL. The SLAC experiments permit further exploration of the multi-GeV/m envelope in DWAs, and will entail investigations of novel materials (e.g. CVD diamond) and geometries (Bragg cylindrical structures, slab-symmetric DWAs), and have an over-riding goal ofmore » demonstrating >GeV acceleration in {approx}33 cm DWA tubes. In the nearer term before FACET's commissioning, we are planning measurements at the BNL ATF, in which we drive {approx}50-200 MV/m fields with single pulses or pulse trains. These experiments are of high relevance to enhancing linear collider DWA designs, as they will demonstrate potential for efficient operation with pulse trains.« less

RF-photonic chirp encoder and compressor for seamless analysis of information flow.

PubMed

Zalevsky, Zeev; Shemer, Amir; Zach, Shlomo

2008-05-26

In this paper we realize an RF photonic chirp compression system that compresses a continuous stream of incoming RF data (modulated on top of an optical carrier) into a train of temporal short pulses. Each pulse in the train can be separated and treated individually while being sampled by low rate optical switch and without temporal loses of the incoming flow of information. Each such pulse can be filtered and analyzed differently. The main advantage of the proposed system is its capability of being able to handle, seamlessly, high rate information flow with all-optical means and with low rate optical switches.

Generation of light and dark soliton trains in a dissipative four-wave mixing, mode-locked fibre ring laser

NASA Astrophysics Data System (ADS)

Zolotovskii, I. O.; Korobko, D. A.; Sysolyatin, A. A.

2018-02-01

We consider a model of a dissipative four-wave mixing, mode-locked fibre ring laser with an intracavity interferometer. The necessary conditions required for mode locking are presented. A pulse train generation is numerically simulated at different repetition rates and gain levels. Admissible ranges of values, for which successful mode locking is possible, are found. It is shown that in the case of normal dispersion of the resonator, a laser with an intracavity interferometer can generate a train of pulses with an energy much greater than that in the case of anomalous dispersion.

Nd:YAP laser pulse compression by three-stage transient stimulated Brillouin and Raman scattering

NASA Astrophysics Data System (ADS)

Kubeček, V.; Hamal, K.; Procházka, I.; Buzelis, R.; Girdauskas, V.; Dementiev, A.

1991-08-01

There is a continuous effort to generate stable, powerful picosecond laser pulses for application in spectroscopy, nonlinear optics and parametric light generation, as well. One of the possible methods is the compression of longer nanosecond laser pulses by stimulated Brillouin and stimulated Raman scattering. The advantages of such a technique, in comparison to the used mode locked picosecond lasers, are as follows: the absence of the active and/or passive mode lockers used to generate a train of picosecond pulses, and the absence of a fast electrooptical shutter used to select a single pulse from a train of pulses. The application of stimulated Brillouin and stimulated Raman scattering permits to generate picosecond pulses in the wavelength regions not covered by mode locked lasers. Of special interest is the wavelength region of 0·8 μm, which may be amplified by the attractive Titanium Sapphire lasers. In this paper we are summarizing our results in theoretical modelling and in real generation of picosecond pulses by means of cascaded stimulated Brillouin and Raman scattering. The models of scattering processes have been investigated. The stable generation of 5, 7, 3 picosecond pulses have been optimized for the wavelengths of 0·8, 0·64 and 0·54 μm, respectively. In all these cases, the pulses exhibited the far field pattern close to Gaussian, with the pulse energy ranging from 0·2 to 1 mJ.

Across-site patterns of modulation detection: Relation to speech recognitiona)

PubMed Central

Garadat, Soha N.; Zwolan, Teresa A.; Pfingst, Bryan E.

2012-01-01

The aim of this study was to identify across-site patterns of modulation detection thresholds (MDTs) in subjects with cochlear implants and to determine if removal of sites with the poorest MDTs from speech processor programs would result in improved speech recognition. Five hundred millisecond trains of symmetric-biphasic pulses were modulated sinusoidally at 10 Hz and presented at a rate of 900 pps using monopolar stimulation. Subjects were asked to discriminate a modulated pulse train from an unmodulated pulse train for all electrodes in quiet and in the presence of an interleaved unmodulated masker presented on the adjacent site. Across-site patterns of masked MDTs were then used to construct two 10-channel MAPs such that one MAP consisted of sites with the best masked MDTs and the other MAP consisted of sites with the worst masked MDTs. Subjects’ speech recognition skills were compared when they used these two different MAPs. Results showed that MDTs were variable across sites and were elevated in the presence of a masker by various amounts across sites. Better speech recognition was observed when the processor MAP consisted of sites with best masked MDTs, suggesting that temporal modulation sensitivity has important contributions to speech recognition with a cochlear implant. PMID:22559376

Generation of straight-line shifting bright-dark soliton trains with a wide dip in the symmetric center or dark solitons in optical fibers

NASA Astrophysics Data System (ADS)

Zhong, Xianqiong; Yao, Na; Sheng, Jia'nan; Cheng, Ke

2018-02-01

Nonlinear evolutions of dark soliton pulses with initially constant frequency chirps are investigated numerically for different soliton orders and chirp parameters in different dispersion regimes of optical fibers. The results show interestingly that, in the normal dispersion regime, the evolution properties remain unchanged apart from their straight-line shifts of the temporal trajectories compared with the chirp-free case. While in the anomalous dispersion regime, the dark solitons can evolve to bright-dark soliton trains with a wide black soliton in the symmetric center. The longer the distance, the more the pulse number. The larger the soliton order, the more the pulse number at the same distance. Similarly, straight-line shift of the temporal trajectory of the bright-dark soliton trains will also appear. The shifting amount and direction depend on the absolute value and the sign of the chirp parameter, respectively. This result inspires people to generate bright-dark soliton trains by using ordinary passive optical fibers instead of fiber lasers. Besides, this work also provides us an alternative approach to guide the formed solitons or soliton trains to move their temporal trajectories along straight lines.

Pulse width modulation inverter with battery charger

DOEpatents

Slicker, James M.

1985-01-01

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a microprocessor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .theta., where .theta. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands for electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a "flyback" DC-DC converter circuit for recharging the battery.

Pulse width modulation inverter with battery charger

NASA Technical Reports Server (NTRS)

Slicker, James M. (Inventor)

1985-01-01

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a microprocessor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .theta., where .theta. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands for electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a flyback DC-DC converter circuit for recharging the battery.

Impact of medical training and clinical experience on the assessment of oxygenation and hypoxaemia after general anaesthesia: an observational study.

PubMed

Aust, Hansjörg; Kranke, Peter; Eberhart, Leopold H J; Afshari, Arash; Weber, Frank; Brieskorn, Melanie; Heine, Julian; Arndt, Christian; Rüsch, Dirk

2015-06-01

In Germany it is common practice to use pulse oximetry and supplementary oxygen only on request in patients breathing spontaneously transferred to the post-anaesthesia care unit (PACU) following surgery under general anaesthesia. The main aim was to study the influence of medical training and clinical experience on assessing SpO(2) and detecting hypoxaemia in these patients. The second aim was to do a preliminary assessment whether this practice can be found in countries other than Germany. Anaesthetists, nurses and medical students estimated SpO(2) in patients breathing room air at the end of transfer to the PACU following surgery (including all major surgical fields) under general anaesthesia. Estimated SpO(2) was compared to SpO(2) measured by pulse oximetry. A survey was carried out among European anaesthesists concerning the use of pulse oximetry and supplementary oxygen during patient transfer to the PACU. Hypoxaemia (SpO(2) < 90 %) occurred in 154 (13.5 %) out of 1,138 patients. Anaesthetists, nurses, and medical students identified only 25, 23, and 21 patients of those as being hypoxaemic, respectively. Clinical experience did not improve detection of hypoxaemia both in anaesthetists (p = 0.63) and nurses (p = 0.18). Use of pulse oximetry and supplemental oxygen during patient transfer to the PACU in European countries differs to a large extent. It seems to be applied only on request in many hospitals. Considering the uncertainty about deleterious effects of transient, short lasting hypoxaemia routine use of pulse oximetry is advocated for patient transfer to the PACU.

Interaction of an ultrarelativistic electron bunch train with a W-band accelerating structure: High power and high gradient

DOE PAGES

Wang, D.; Antipov, S.; Jing, C.; ...

2016-02-05

Electron beam interaction with high frequency structures (beyond microwave regime) has a great impact on future high energy frontier machines. We report on the generation of multimegawatt pulsed rf power at 91 GHz in a planar metallic accelerating structure driven by an ultrarelativistic electron bunch train. This slow-wave wakefield device can also be used for high gradient acceleration of electrons with a stable rf phase and amplitude which are controlled by manipulation of the bunch train. To achieve precise control of the rf pulse properties, a two-beam wakefield interferometry method was developed in which the rf pulse, due to themore » interference of the wakefields from the two bunches, was measured as a function of bunch separation. As a result, measurements of the energy change of a trailing electron bunch as a function of the bunch separation confirmed the interferometry method.« less

UltraPulse--simulating a human arterial pulse with focussed airborne ultrasound.

PubMed

Hung, G M Y; John, N W; Hancock, C; Gould, D A; Hoshi, T

2013-01-01

Medical simulators provide a risk-free environment for trainee doctors to practice and improve their skills. UltraPulse is a new tactile system designed to utilise focussed airborne ultrasound to mimic a pulsation effect such as that of a human arterial pulse. In this paper, we focus on the construction of the haptics component, which can later be integrated into a variety of medical procedure training simulators.

Quasi-phase matching and quantum control of high harmonic generation in waveguides using counterpropagating beams

DOEpatents

Zhang, Xiaoshi; Lytle, Amy L.; Cohen, Oren; Kapteyn, Henry C.; Murnane, Margaret M.

2010-11-09

All-optical quasi-phase matching (QPM) uses a train of counterpropagating pulses to enhance high-order harmonic generation (HHG) in a hollow waveguide. A pump pulse enters one end of the waveguide, and causes HHG in the waveguide. The counterpropagation pulses enter the other end of the waveguide and interact with the pump pulses to cause QPM within the waveguide, enhancing the HHG.

Stochastic analysis of a pulse-type prey-predator model

NASA Astrophysics Data System (ADS)

Wu, Y.; Zhu, W. Q.

2008-04-01

A stochastic Lotka-Volterra model, a so-called pulse-type model, for the interaction between two species and their random natural environment is investigated. The effect of a random environment is modeled as random pulse trains in the birth rate of the prey and the death rate of the predator. The generalized cell mapping method is applied to calculate the probability distributions of the species populations at a state of statistical quasistationarity. The time evolution of the population densities is studied, and the probability of the near extinction time, from an initial state to a critical state, is obtained. The effects on the ecosystem behaviors of the prey self-competition term and of the pulse mean arrival rate are also discussed. Our results indicate that the proposed pulse-type model shows obviously distinguishable characteristics from a Gaussian-type model, and may confer a significant advantage for modeling the prey-predator system under discrete environmental fluctuations.

Stochastic analysis of a pulse-type prey-predator model.

PubMed

Wu, Y; Zhu, W Q

2008-04-01

A stochastic Lotka-Volterra model, a so-called pulse-type model, for the interaction between two species and their random natural environment is investigated. The effect of a random environment is modeled as random pulse trains in the birth rate of the prey and the death rate of the predator. The generalized cell mapping method is applied to calculate the probability distributions of the species populations at a state of statistical quasistationarity. The time evolution of the population densities is studied, and the probability of the near extinction time, from an initial state to a critical state, is obtained. The effects on the ecosystem behaviors of the prey self-competition term and of the pulse mean arrival rate are also discussed. Our results indicate that the proposed pulse-type model shows obviously distinguishable characteristics from a Gaussian-type model, and may confer a significant advantage for modeling the prey-predator system under discrete environmental fluctuations.

Automated cardiopulmonary resuscitation using a load-distributing band external cardiac support device for in-hospital cardiac arrest: a single centre experience of AutoPulse-CPR.

PubMed

Spiro, J R; White, S; Quinn, N; Gubran, C J; Ludman, P F; Townend, J N; Doshi, S N

2015-02-01

Poor quality cardiopulmonary resuscitation (CPR) predicts adverse outcome. During invasive cardiac procedures automated-CPR (A-CPR) may help maintain effective resuscitation. The use of A-CPR following in-hospital cardiac arrest (IHCA) remains poorly described. Firstly, we aimed to assess the efficiency of healthcare staff using A-CPR in a cardiac arrest scenario at baseline, following re-training and over time (Scenario-based training). Secondly, we studied our clinical experience of A-CPR at our institution over a 2-year period, with particular emphasis on the details of invasive cardiac procedures performed, problems encountered, resuscitation rates and in-hospital outcome (AutoPulse-CPR Registry). Scenario-based training: Forty healthcare professionals were assessed. At baseline, time-to-position device was slow (mean 59 (±24) s (range 15-96s)), with the majority (57%) unable to mode-switch. Following re-training time-to-position reduced (28 (±9) s, p<0.01 vs baseline) with 95% able to mode-switch. This improvement was maintained over time. AutoPulse-CPR Registry: 285 patients suffered IHCA, 25 received A-CPR. Survival to hospital discharge following conventional CPR was 28/260 (11%) and 7/25 (28%) following A-CPR. A-CPR supported invasive procedures in 9 patients, 2 of whom had A-CPR dependant circulation during transfer to the catheter lab. A-CPR may provide excellent haemodynamic support and facilitate simultaneous invasive cardiac procedures. A significant learning curve exists when integrating A-CPR into clinical practice. Further studies are required to better define the role and effectiveness of A-CPR following IHCA. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Laser bandwidth interlock capable of single pulse detection and rejection

DOEpatents

Armstrong, James P; Telford, Steven James; Lanning, Rodney Kay; Bayramian, Andrew James

2012-10-09

A pulse of laser light is switched out of a pulse train and spatially dispersed into its constituent wavelengths. The pulse is collimated to a suitable size and then diffracted by high groove density multilayer dielectric gratings. This imparts a different angle to each individual wavelength so that, when brought to the far field with a lens, the colors have spread out in a linear arrangement. The distance between wavelengths (resolution) can be tailored for the specific laser and application by altering the number of times the beam strikes the diffraction gratings, the groove density of the gratings and the focal length of the lens. End portions of the linear arrangement are each directed to a respective detector, which converts the signal to a 1 if the level meets a set-point, and a 0 if the level does not. If both detectors produces a 1, then the pulse train is allowed to propagate into an optical system.

Spatial performance correlates with in vitro potentiation in young and aged Fischer 344 rats.

PubMed

Deupree, D L; Turner, D A; Watters, C L

1991-07-19

Young adult (2-4 months old) and aged (24-26 months old) Fischer 344 (F344) rats were trained for spatial behavior (locating a hidden escape platform) in a circular water maze. The aged rats showed deficits in both the acquisition and retention of the learned response. Following the behavioral training, hippocampal slices from the rats were prepared. Potentiation of CA1 extracellular, somatic field potentials was studied in vitro following either a short stimulus train (4 pulses) or a longer train (50 pulses). Slices from the aged rats showed less short-term potentiation (124.8 +/- 4.9% baseline, mean +/- S.E.M.) at 1 min following the short train in comparison to slices from the young rats (151.8 +/- 7.5%, P less than 0.05). However, following the longer train, no differences were found between the groups in the degree of either short-term (measured at 1 min after stimulation) or long-term potentiation (measured at 60 min). The amount of potentiation seen at various time points after either train correlated with the behavioral measure of retention. These results indicate that F344 rats exhibit age-related behavioral deficits, and age-related synaptic potentiation deficits in response to short stimulation trains. The correlation between the degree of potentiation (both short-term and long-term) and retention of a behavioral task adds strength to the hypothesis that potentiation mechanisms may underlie memory processes.

A bright attosecond x-ray pulse train generation in a double-laser-driven cone target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hu, Li-Xiang; Yu, Tong-Pu, E-mail: tongpu@nudt.edu.cn; Shao, Fu-Qiu

By using full three-dimensional particle-in-cell and Monte Carlo simulations, we investigate the generation of a high-brightness attosecond x-ray pulse train in a double-laser-driven cone target. The scheme makes use of two lasers: the first high-intensity laser with a laser peak intensity 1.37 × 10{sup 20 }W/cm{sup 2} irradiates the cone and produces overdense attosecond electron bunches; the second counterpropagating weakly relativistic laser with a laser peak intensity 4.932 × 10{sup 17 }W/cm{sup 2} interacts with the produced electron bunches and a bright x-ray pulse train is generated by Thomson backscattering of the second laser off the attosecond electron bunches. It is shown that the photon fluxmore » rises by 5 times using the cone target as compared with a normal channel. Meanwhile, the x-ray peak brightness increases significantly from 1.4 × 10{sup 21}/(s mm{sup 2} mrad{sup 2} 0.1 keV) to 6.0 × 10{sup 21}/(s mm{sup 2} mrad{sup 2} 0.1 keV), which is much higher than that of the Thomson x-ray source generated from traditional accelerators. We also discuss the influence of the laser and target parameters on the x-ray pulse properties. This compact bright x-ray source may have diverse applications, e.g., the study of electric dynamics and harmonics emission in the atomic scale.« less

[Autogenic training as a therapy for adjustment disorder in adolescents].

PubMed

Jojić, Boris R; Leposavić, Ljubica M

2005-01-01

Autogenic training is a widespread technique used in psychotherapy. The British school of autogenic training cites a large list of diseases, health states, and life changes, in which autogenic training can be of help. We wanted to explore the application of autogenic training as a therapy for adjustment disorder in adolescents. The sample consisted of a homogeneous group of 31 individuals, with an average age of 17.3 +/- 0.2 years, who were diagnosed with adjustment disorder, F 43.2, in accordance with ICD 10 search criteria. The aim of our work was to figure out the influence of autogenic training on adjustment disorder, through biophysical and biochemical indicators, and to research the efficiacy of autogenic training as a therapy for adjustment disorder in adolescents. We observed adjustment disorder indicators and their changes in three phases, using initial, final, and control values, which we measured immediately before the beginning, immediately after the completion, and six months after the completion, of the practical course in autogenic training. We measured systolic and diastolic arterial blood pressure, brachial pulse rates, cortisol levels in plasma, cholesterol levels in blood, as well as glucose concentrations. During that period, autogenic training was employed as the sole therapy. The study confirmed our preliminary assumptions. The measurements we performed showed that arterial blood pressure, pulse rates, cholesterol and cortisol concentrations, after the application of autogenic training among adolescents suffering from adjustment disorder, were lower than the initial values. They remained lower even six months after the completion of the practical course in autogenic training. We concluded that autogenic training significantly decreases the values of physiological indicators of adjustment disorder, diminishes the effects of stress in an individual, and eases the adaptation of adolescents to stress, helping with recovery.

Physical Training, Hemodynamic Parameters and Arterial Stiffness: Friends or Foes of the Hypertensive Patient?

PubMed

Iurciuc, Stela; Avram, Claudiu; Turi, Vladiana; Militaru, Anda; Avram, Adina; Cimpean, Anca Maria; Iurciuc, Mircea

2016-01-01

To evaluate the impact of physical training on central hemodynamic parameters and elasticity of large arteries in hypertensive patients. A total of 129 hypertensive patients were divided into two groups: group A followed lifestyle changes and physical training; and group B acted as a control group; seven parameters were recorded: Pulse wave velocity (PWVao), systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), central aortic systolic blood pressure (SBPao), aortic diastolic blood pressure (DBPao), and central aortic pulse pressure (PPao). The difference between values at 4 months and baseline (Δ) were as follows: ΔPWVao was -1.02 m/s (p<0.001) versus 0.17 m/s (p=0.035), ΔSBPao was -9.6 mmHg (p=0.009) versus 1.6 mmHg (p=0.064), and ΔPPao was -6.8 mmHg (p<0.001) versus 3.2 mmHg, (p=0.029) in group A versus B, respectively. Exercise training improves SBP, PP, SBPao, PPao and may delay arterial ageing. Copyright © 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

Effect of tendon vibration during wide-pulse neuromuscular electrical stimulation (NMES) on muscle force production in people with spinal cord injury (SCI).

PubMed

Bochkezanian, Vanesa; Newton, Robert U; Trajano, Gabriel S; Vieira, Amilton; Pulverenti, Timothy S; Blazevich, Anthony J

2018-02-13

Neuromuscular electrical stimulation (NMES) is commonly used in skeletal muscles in people with spinal cord injury (SCI) with the aim of increasing muscle recruitment and thus muscle force production. NMES has been conventionally used in clinical practice as functional electrical stimulation (FES), using low levels of evoked force that cannot optimally stimulate muscular strength and mass improvements, and thus trigger musculoskeletal changes in paralysed muscles. The use of high intensity intermittent NMES training using wide-pulse width and moderate-intensity as a strength training tool could be a promising method to increase muscle force production in people with SCI. However, this type of protocol has not been clinically adopted because it may generate rapid muscle fatigue and thus prevent the performance of repeated high-intensity muscular contractions in paralysed muscles. Moreover, superimposing patellar tendon vibration onto the wide-pulse width NMES has been shown to elicit further increases in impulse or, at least, reduce the rate of fatigue in repeated contractions in able-bodied populations, but there is a lack of evidence to support this argument in people with SCI. Nine people with SCI received two NMES protocols with and without superimposing patellar tendon vibration on different days (i.e. STIM and STIM+vib), which consisted of repeated 30 Hz trains of 58 wide-pulse width (1000 μs) symmetric biphasic pulses (0.033-s inter-pulse interval; 2 s stimulation train; 2-s inter-train interval) being delivered to the dominant quadriceps femoris. Starting torque was 20% of maximal doublet-twitch torque and stimulations continued until torque declined to 50% of the starting torque. Total knee extensor impulse was calculated as the primary outcome variable. Total knee extensor impulse increased in four subjects when patellar tendon vibration was imposed (59.2 ± 15.8%) but decreased in five subjects (- 31.3 ± 25.7%). However, there were no statistically significant differences between these sub-groups or between conditions when the data were pooled. Based on the present results there is insufficient evidence to conclude that patellar tendon vibration provides a clear benefit to muscle force production or delays muscle fatigue during wide-pulse width, moderate-intensity NMES in people with SCI. ACTRN12618000022268 . Date: 11/01/2018. Retrospectively registered.

High-power noise-like pulse generation using a 1.56-µm all-fiber laser system.

PubMed

Lin, Shih-Shian; Hwang, Sheng-Kwang; Liu, Jia-Ming

2015-07-13

We demonstrated an all-fiber, high-power noise-like pulse laser system at the 1.56-µm wavelength. A low-power noise-like pulse train generated by a ring oscillator was amplified using a two-stage amplifier, where the performance of the second-stage amplifier determined the final output power level. The optical intensity in the second-stage amplifier was managed well to avoid not only the excessive spectral broadening induced by nonlinearities but also any damage to the device. On the other hand, the power conversion efficiency of the amplifier was optimized through proper control of its pump wavelength. The pump wavelength determines the pump absorption and therefore the power conversion efficiency of the gain fiber. Through this approach, the average power of the noise-like pulse train was amplified considerably to an output of 13.1 W, resulting in a power conversion efficiency of 36.1% and a pulse energy of 0.85 µJ. To the best of our knowledge, these amplified pulses have the highest average power and pulse energy for noise-like pulses in the 1.56-µm wavelength region. As a result, the net gain in the cascaded amplifier reached 30 dB. With peak and pedestal widths of 168 fs and 61.3 ps, respectively, for the amplified pulses, the pedestal-to-peak intensity ratio of the autocorrelation trace remains at the value of 0.5 required for truly noise-like pulses.

Carrier-envelope phase-stabilized attosecond pulses from asymmetric molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan Pengfei; Lu Peixiang; Cao Wei

2007-08-15

High-order harmonic generation from asymmetric molecules is investigated, and the concept of phase-stabilized infrared ultrashort laser pulses is extended to the extreme ultraviolet regime. It is shown that the ionization symmetry in consecutive half optical cycles is broken for asymmetric molecules, and both even and odd harmonics with comparable intensity are produced. In the time domain, only one attosecond pulse is generated in each cycle of the driving field, and the carrier-envelope phases of the attosecond pulses are equal. Consequently, a clean attosecond pulse train with the same carrier-envelope phase from pulse to pulse is obtained in the extreme ultravioletmore » regime.« less

A System Approach to Navy Medical Education and Training. Appendix 22. Otolaryngology Technician.

DTIC Science & Technology

1974-08-31

PROCEDURES TO PATIENT 12 PEXPLAIN LUMBAR PUNCTURE PROCEDURES TO PATIENT 13 IMEASURE/WEIGH PATIENT OR PERSONNEL 14 ICHECK CENTRAL VENOUS PRESSURE 15 TAKE...BLOOD PRESSURE 16 [CHECK RADIAL AWRIST) PULSE 17 ICHECK FEMORAL PULSE FOR PRESENCE AND QUALITY 8 IDETERMINE APICAL PULSE RATE/RHYTHM WITH STETHESCOPE 19... ICHECK PATIENTS TEMPERATURE 2U ICHECK /COUNT RESPIRATIONS 21 IPERFORM CIRCULATION CHECK, E.G. COLOR, PULSE, TEMPERATURE OF ISKIN, CAPILLARY RETURN 22

The Air Force Geophysics Laboratory Standalone Data Acquisition System: A Functional Description.

DTIC Science & Technology

1980-10-09

the board are a buffer for the RUN/HALT front panel switch and a retriggerable oneshot multivibrator. This latter circuit senses the SRUN pulse train...recording on the data tapes, and providing the master timing source for data acquisition. An Electronic Research Company (ERC) model 2446 digital...the computer is fed to a retriggerable oneshot multivibrator on the board. (SRUN consists of a pulse train that is present when the computer is running

Study of optimal training protocols and devices for developing and maintaining physical fitness in females prior to and during space flight

NASA Technical Reports Server (NTRS)

Olree, H. D.; Corbin, B.; Smith, C.

1977-01-01

Pedalling a bicycle at least ten minutes a day at 85% of maximum pulse rate, three days a week for ten weeks will produce moderate increases in overall strength and physical work capacity in college-age females. The longer the training session, up to thirty minutes per session, the greater are the increases in physical work capacity that result when college-age females are trained three days a week for ten weeks at 85% of their maximum heart rate.

Programmed optoelectronic time-pulse coded relational processor as base element for sorting neural networks

NASA Astrophysics Data System (ADS)

Krasilenko, Vladimir G.; Bardachenko, Vitaliy F.; Nikolsky, Alexander I.; Lazarev, Alexander A.

2007-04-01

In the paper we show that the biologically motivated conception of the use of time-pulse encoding gives the row of advantages (single methodological basis, universality, simplicity of tuning, training and programming et al) at creation and designing of sensor systems with parallel input-output and processing, 2D-structures of hybrid and neuro-fuzzy neurocomputers of next generations. We show principles of construction of programmable relational optoelectronic time-pulse coded processors, continuous logic, order logic and temporal waves processes, that lie in basis of the creation. We consider structure that executes extraction of analog signal of the set grade (order), sorting of analog and time-pulse coded variables. We offer optoelectronic realization of such base relational elements of order logic, which consists of time-pulse coded phototransformers (pulse-width and pulse-phase modulators) with direct and complementary outputs, sorting network on logical elements and programmable commutations blocks. We make estimations of basic technical parameters of such base devices and processors on their basis by simulation and experimental research: power of optical input signals - 0.200-20 μW, processing time - microseconds, supply voltage - 1.5-10 V, consumption power - hundreds of microwatts per element, extended functional possibilities, training possibilities. We discuss some aspects of possible rules and principles of training and programmable tuning on the required function, relational operation and realization of hardware blocks for modifications of such processors. We show as on the basis of such quasiuniversal hardware simple block and flexible programmable tuning it is possible to create sorting machines, neural networks and hybrid data-processing systems with the untraditional numerical systems and pictures operands.

Behavioral assessment of sensitivity to intracortical microstimulation of primate somatosensory cortex.

PubMed

Kim, Sungshin; Callier, Thierri; Tabot, Gregg A; Gaunt, Robert A; Tenore, Francesco V; Bensmaia, Sliman J

2015-12-08

Intracortical microstimulation (ICMS) is a powerful tool to investigate the functional role of neural circuits and may provide a means to restore sensation for patients for whom peripheral stimulation is not an option. In a series of psychophysical experiments with nonhuman primates, we investigate how stimulation parameters affect behavioral sensitivity to ICMS. Specifically, we deliver ICMS to primary somatosensory cortex through chronically implanted electrode arrays across a wide range of stimulation regimes. First, we investigate how the detectability of ICMS depends on stimulation parameters, including pulse width, frequency, amplitude, and pulse train duration. Then, we characterize the degree to which ICMS pulse trains that differ in amplitude lead to discriminable percepts across the range of perceptible and safe amplitudes. We also investigate how discriminability of pulse amplitude is modulated by other stimulation parameters-namely, frequency and duration. Perceptual judgments obtained across these various conditions will inform the design of stimulation regimes for neuroscience and neuroengineering applications.

REVIEW ARTICLE: Harmonically mode-locked semiconductor-based lasers as high repetition rate ultralow noise pulse train and optical frequency comb sources

NASA Astrophysics Data System (ADS)

Quinlan, F.; Ozharar, S.; Gee, S.; Delfyett, P. J.

2009-10-01

Recent experimental work on semiconductor-based harmonically mode-locked lasers geared toward low noise applications is reviewed. Active, harmonic mode-locking of semiconductor-based lasers has proven to be an excellent way to generate 10 GHz repetition rate pulse trains with pulse-to-pulse timing jitter of only a few femtoseconds without requiring active feedback stabilization. This level of timing jitter is achieved in long fiberized ring cavities and relies upon such factors as low noise rf sources as mode-lockers, high optical power, intracavity dispersion management and intracavity phase modulation. When a high finesse etalon is placed within the optical cavity, semiconductor-based harmonically mode-locked lasers can be used as optical frequency comb sources with 10 GHz mode spacing. When active mode-locking is replaced with regenerative mode-locking, a completely self-contained comb source is created, referenced to the intracavity etalon.

Cell Electrosensitization Exists Only in Certain Electroporation Buffers.

PubMed

Dermol, Janja; Pakhomova, Olga N; Pakhomov, Andrei G; Miklavčič, Damijan

2016-01-01

Electroporation-induced cell sensitization was described as the occurrence of a delayed hypersensitivity to electric pulses caused by pretreating cells with electric pulses. It was achieved by increasing the duration of the electroporation treatment at the same cumulative energy input. It could be exploited in electroporation-based treatments such as electrochemotherapy and tissue ablation with irreversible electroporation. The mechanisms responsible for cell sensitization, however, have not yet been identified. We investigated cell sensitization dynamics in five different electroporation buffers. We split a pulse train into two trains varying the delay between them and measured the propidium uptake by fluorescence microscopy. By fitting the first-order model to the experimental results, we determined the uptake due to each train (i.e. the first and the second) and the corresponding resealing constant. Cell sensitization was observed in the growth medium but not in other tested buffers. The effect of pulse repetition frequency, cell size change, cytoskeleton disruption and calcium influx do not adequately explain cell sensitization. Based on our results, we can conclude that cell sensitization is a sum of several processes and is buffer dependent. Further research is needed to determine its generality and to identify underlying mechanisms.

Cell Electrosensitization Exists Only in Certain Electroporation Buffers

PubMed Central

Dermol, Janja; Pakhomova, Olga N.; Pakhomov, Andrei G.; Miklavčič, Damijan

2016-01-01

Electroporation-induced cell sensitization was described as the occurrence of a delayed hypersensitivity to electric pulses caused by pretreating cells with electric pulses. It was achieved by increasing the duration of the electroporation treatment at the same cumulative energy input. It could be exploited in electroporation-based treatments such as electrochemotherapy and tissue ablation with irreversible electroporation. The mechanisms responsible for cell sensitization, however, have not yet been identified. We investigated cell sensitization dynamics in five different electroporation buffers. We split a pulse train into two trains varying the delay between them and measured the propidium uptake by fluorescence microscopy. By fitting the first-order model to the experimental results, we determined the uptake due to each train (i.e. the first and the second) and the corresponding resealing constant. Cell sensitization was observed in the growth medium but not in other tested buffers. The effect of pulse repetition frequency, cell size change, cytoskeleton disruption and calcium influx do not adequately explain cell sensitization. Based on our results, we can conclude that cell sensitization is a sum of several processes and is buffer dependent. Further research is needed to determine its generality and to identify underlying mechanisms. PMID:27454174

On the use of a chirped Bragg grating as a cavity mirror of a picosecond Nd : YAG laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zubko, A E; Shashkov, E V; Smirnov, A V

2016-02-28

The first experimental evidence is presented that the use of a chirped volume Bragg grating (CVBG) as a cavity mirror of a Q-switched picosecond Nd : YAG laser with self-mode-locking leads to significant changes in the temporal parameters of the laser output. Measurements have been performed at two positions of the CVBG: with the grating placed so that shorter wavelengths reflected from its front part lead longer wavelengths or with the grating rotated through 180°, so that longer wavelengths are reflected first. In the former case, the duration of individual pulses in a train increased from ∼35 to ∼300 ps,more » whereas the pulse train shape and duration remained the same as in the case of a conventional laser with a mirror cavity. In the latter case, the full width at half maximum of pulse trains increased from ∼70 ns (Nd : YAG laser with a mirror cavity) to ∼1 ms, and the duration of individual pulses increased from 35 ps to ∼1.2 ns, respectively, which is more typical of free-running laser operation. (laser crystals and braggg ratings)« less

Method and apparatus for pulse width modulation control of an AC induction motor

DOEpatents

Geppert, Steven; Slicker, James M.

1984-01-01

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a "flyback" DC-DC converter circuit for recharging the battery.

Sensitivity to binaural timing in bilateral cochlear implant users.

PubMed

van Hoesel, Richard J M

2007-04-01

Various measures of binaural timing sensitivity were made in three bilateral cochlear implant users, who had demonstrated moderate-to-good interaural time delay (ITD) sensitivity at 100 pulses-per-second (pps). Overall, ITD thresholds increased at higher pulse rates, lower levels, and shorter durations, although intersubject differences were evident. Monaural rate-discrimination thresholds, using the same stimulation parameters, showed more substantial elevation than ITDs with increased rate. ITD sensitivity with 6000 pps stimuli, amplitude-modulated at 100 Hz, was similar to that with unmodulated pulse trains at 100 pps, but at 200 and 300 Hz performance was poorer than with unmodulated signals. Measures of sensitivity to binaural beats with unmodulated pulse-trains showed that all three subjects could use time-varying ITD cues at 100 pps, but not 300 pps, even though static ITD sensitivity was relatively unaffected over that range. The difference between static and dynamic ITD thresholds is discussed in terms of relative contributions from initial and later arriving cues, which was further examined in an experiment using two-pulse stimuli as a function of interpulse separation. In agreement with the binaural-beat data, findings from that experiment showed poor discrimination of ITDs on the second pulse when the interval between pulses was reduced to a few milliseconds.

Method and apparatus for pulse width modulation control of an AC induction motor

NASA Technical Reports Server (NTRS)

Geppert, Steven (Inventor); Slicker, James M. (Inventor)

1984-01-01

An inverter is connected between a source of DC power and a three-phase AC induction motor, and a micro-processor-based circuit controls the inverter using pulse width modulation techniques. In the disclosed method of pulse width modulation, both edges of each pulse of a carrier pulse train are equally modulated by a time proportional to sin .THETA., where .THETA. is the angular displacement of the pulse center at the motor stator frequency from a fixed reference point on the carrier waveform. The carrier waveform frequency is a multiple of the motor stator frequency. The modulated pulse train is then applied to each of the motor phase inputs with respective phase shifts of 120.degree. at the stator frequency. Switching control commands of electronic switches in the inverter are stored in a random access memory (RAM) and the locations of the RAM are successively read out in a cyclic manner, each bit of a given RAM location controlling a respective phase input of the motor. The DC power source preferably comprises rechargeable batteries and all but one of the electronic switches in the inverter can be disabled, the remaining electronic switch being part of a flyback DC-DC converter circuit for recharging the battery.

Exercise training in adults with repaired tetralogy of Fallot: A randomized controlled pilot study of continuous versus interval training.

PubMed

Novaković, Marko; Prokšelj, Katja; Rajkovič, Uroš; Vižintin Cuderman, Tjaša; Janša Trontelj, Katja; Fras, Zlatko; Jug, Borut

2018-03-15

Adults with repaired tetralogy of Fallot (ToF) have impaired exercise capacity, vascular and cardiac autonomic function, and quality of life (QoL). Specific effects of high-intensity interval or moderate continuous exercise training on these parameters in adults with repaired ToF remain unknown. Thirty adults with repaired ToF were randomized to either high-intensity interval, moderate intensity continuous training (36 sessions, 2-3 times a week) or usual care (no supervised exercise). Exercise capacity, flow-mediated vasodilation, pulse wave velocity, NT-proBNP and fibrinogen levels, heart rate variability and recovery, and QoL (SF-36 questionnaire) were determined at baseline and after the intervention period. Twenty-seven patients (mean age 39±9years, 63% females, 9 from each group) completed this pilot study. Both training groups improved in at least some parameters of cardiovascular health compared to no exercise. Interval-but not continuous-training improved VO2peak (21.2 to 22.9ml/kg/min, p=0.004), flow-mediated vasodilation (8.4 to 12.9%, p=0.019), pulse wave velocity (5.4 to 4.8m/s, p=0.028), NT-proBNP (202 to 190ng/L, p=0.032) and fibrinogen levels (2.67 to 2.46g/L, p=0.018). Conversely, continuous-but not interval-training improved heart rate variability (low-frequency domain, 0.32 to 0.22, p=0.039), heart rate recovery after 2min post-exercise (40 to 47 beats, p=0.023) and mental domain of SF-36 (87 to 95, p=0.028). Both interval and continuous exercise training modalities were safe. Interval training seems more efficacious in improving exercise capacity, vascular function, NT-proBNP and fibrinogen levels, while continuous training seems more efficacious in improving cardiac autonomic function and QoL. (Clinicaltrials.gov, NCT02643810). Copyright © 2018 Elsevier Ireland Ltd. All rights reserved.

Birefringence profile adjustment by spatial overlap of nanogratings induced by ultra-short laser pulses inside fused silica

NASA Astrophysics Data System (ADS)

Arabanian, Atoosa Sadat; Najafi, Somayeh; Ajami, Aliasghar; Husinsky, Wolfgang; Massudi, Reza

2018-02-01

We have succeeded in realizing a method to control the spatial distribution of optical retardation as a result of nanogratings in bulk-fused silica induced by ultrashort laser pulses. A colorimetry-based retardation measurement (CBRM) based on the Michel-Levy interference color chart using a polarization microscope is used to determine the profiles of the optical retardation. Effects of the spatial overlap of written regions as well as the energy and polarization of the writing pulses on the induced retardations are studied. It has been found that the spatial overlap of lines written by pulse trains with different energies and polarizations can result in an adjustment of the induced birefringence in the overlap region. This approach offers the possibility of designing polarization-sensitive components with a desired birefringence profile.

Feasibility study on a short-pulsed IR wavelength for effective calculus fragmentation

NASA Astrophysics Data System (ADS)

Kang, Hyun Wook

2015-05-01

Laser-induced lithotripsy has been used for a minimally-invasive surgery to treat kidney-stone disease associated with urinary obstruction. A short-pulsed Tm:YAG laser (λ = 2.01 µm) was developed to improve fragmentation efficiency and was evaluated with a Ho:YAG laser (λ = 2.12 μm) as to its ablation feature and mass removal rate. Application of a train of sub-microsecond pulses with a lower energy at a frequency of 500 Hz created multiple events of cavitation that accompanied strong acoustic transients. During Tm:YAG irradiation, both high light absorption and secondary photomechanical impacts readily fragmented the calculus into small pieces (< 3 mm) and removed them 130 times faster than photothermal Ho:YAG lithotripsy. The proposed short-pulsed Tm:YAG approach may be an effective lithotripter for treating calculus disease.

Dynamics of shaping ultrashort optical dissipative solitary pulses in the actively mode-locked semiconductor laser with an external long-haul single-mode fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Moreno Zarate, Pedro

2010-02-01

We describe the conditions of shaping regular trains of optical dissipative solitary pulses, excited by multi-pulse sequences of periodic modulating signals, in the actively mode-locked semiconductor laser heterostructure with an external long-haul single-mode silicon fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and linear optical losses. The presented model for the analysis includes three principal contributions associated with the modulated gain, optical losses, as well as linear and nonlinear phase shifts. In fact, the trains of optical dissipative solitary pulses appear within simultaneous presenting and a balance of mutually compensating interactions between the second-order dispersion and cubic-law Kerr nonlinearity as well as between active medium gain and linear optical losses in the combined cavity. Within such a model, a contribution of the nonlinear Ginzburg-Landau operator to shaping the parameters of optical dissipative solitary pulses is described via exploiting an approximate variational procedure involving the technique of trial functions. Finally, the results of the illustrating proof-of-principle experiments are briefly presented and discussed in terms of optical dissipative solitary pulses.

Helicity-selective phase-matching and quasi-phase matching of circularly polarized high-order harmonics: towards chiral attosecond pulses

DOE PAGES

Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; ...

2016-05-23

Phase matching of circularly polarized high-order harmonics driven by counter-rotating bi-chromatic lasers was recently predicted theoretically and demonstrated experimentally. In that work, phase matching was analyzed by assuming that the total energy, spin angular momentum and linear momentum of the photons participating in the process are conserved. Here we propose a new perspective on phase matching of circularly polarized high harmonics. We derive an extended phase matching condition by requiring a new propagation matching condition between the classical vectorial bi-chromatic laser pump and harmonics fields. This allows us to include the influence of the laser pulse envelopes on phase matching.more » Here, we find that the helicity dependent phase matching facilitates generation of high harmonics beams with a high degree of chirality. Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization. Moreover, while the degree of circularity of the most intense pulse approaches unity, all other pulses exhibit reduced circularity. Lastly, this feature suggests the possibility of using a train of attosecond pulses as an isolated attosecond probe for chiral-sensitive experiments.« less

Coupled Optoelectronic Oscillators:. Application to Low-Jitter Pulse Generation

NASA Astrophysics Data System (ADS)

Yu, N.; Tu, M.; Maleki, L.

2002-04-01

Actively mode-locked Erbium-doped fiber lasers (EDFL) have been studied for generating stable ultra-fast pulses (< 2 ps) at high repetition rates (> 5 GHz) [1,2]. These devices can be compact and environmentally stable, quite suitable for fiber-based high-data-rate communications and optical ultra-fast analog-to-digital conversions (ADC) [3]. The pulse-to-pulse jitter of an EDFL-based pulse generator will be ultimately limited by the phase noise of the mode-locking microwave source (typically electronic frequency synthesizers). On the other hand, opto-electronic oscillators (OEO) using fibers have been demonstrated to generate ultra-low phase noise microwaves at 10 GHz and higher [4]. The overall phase noise of an OEO can be much lower than commercially available synthesizers at the offset-frequency range above 100 Hz. Clearly, ultra-low jitter pulses can be generated by taking advantage of the low phase noise of OEOs. In this paper, we report the progress in developing a new low-jitter pulse generator by combing the two technologies. In our approach, the optical oscillator (mode-locked EDFL) and the microwave oscillator (OEO) are coupled through a common Mach-Zehnder (MZ) modulator, thus named coupled opto-electronic oscillator (COEO) [5]. Based on the results of previous OEO study, we can expect a 10 GHz pulse train with jitters less than 10 fs.

An environmental-level, real-time, pulsed photon dosemeter.

PubMed

Olsher, R H; Frymire, A; Gregoire, T

2005-01-01

Radiation sources producing short pulses of photon radiation are widespread. Such sources include electron linear accelerators and field emission impulse generators. It is often desirable to measure leakage and skyshine radiation for these sources in real time and at environmental levels as low as 0.02 microSv per pulse. This note provides an overview of the design and performance of a commercial, real-time, pulsed photon dosemeter (PPD) capable of single-pulse dose measurements over the range from 0.02 to 20 microSv. The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of pulses over a 3 s period. A pulse repetition rate of up to 300 Hz is accommodated.

Gaussian temporal modulation for the behavior of multi-sinc Schell-model pulses in dispersive media

NASA Astrophysics Data System (ADS)

Liu, Xiayin; Zhao, Daomu; Tian, Kehan; Pan, Weiqing; Zhang, Kouwen

2018-06-01

A new class of pulse source with correlation being modeled by the convolution operation of two legitimate temporal correlation function is proposed. Particularly, analytical formulas for the Gaussian temporally modulated multi-sinc Schell-model (MSSM) pulses generated by such pulse source propagating in dispersive media are derived. It is demonstrated that the average intensity of MSSM pulses on propagation are reshaped from flat profile or a train to a distribution with a Gaussian temporal envelope by adjusting the initial correlation width of the Gaussian pulse. The effects of the Gaussian temporal modulation on the temporal degree of coherence of the MSSM pulse are also analyzed. The results presented here show the potential of coherence modulation for pulse shaping and pulsed laser material processing.

Fifteen terawatt picosecond CO2 laser system.

PubMed

Haberberger, D; Tochitsky, S; Joshi, C

2010-08-16

The generation of a record peak-power of 15 TW (45 J, 3 ps) in a single CO(2) laser beam is reported. Using a master oscillator-power amplifier laser system, it is shown that up to 100 J of energy can be extracted in a train of 3 ps laser pulses separated by 18 ps, a characteristic time of the CO(2) molecule. The bandwidth required for amplifying the short injected laser pulse train in a 2.5 atm final CO(2) amplifier is provided by field broadening of the medium at intensities of up to 140 GW/cm(2). The measured saturation energy for 3 ps pulses is 120 mJ/cm(2) which confirms that energy is simultaneously extracted from six rovibrational lines.

Personnel electronic neutron dosimeter

DOEpatents

Falk, R.B.; Tyree, W.H.

1982-03-03

A personnel electronic dosimeter includes a neutron-proton and neutron-alpha converter for providing an electrical signal having a magnitude proportional to the energy of a detected proton or alpha particle produced from the converter, a pulse generator circuit for generating a pulse having a duration controlled by the weighed effect of the amplitude of the electrical signal, an oscillator enabled by the pulse for generating a train of clock pulses for a time dependent upon the pulse length, a counter for counting the clock pulses, and an indicator for providing a direct reading and aural alarm when the count indicates that the wearer has been exposed to a selected level of neutron dose equivalent.

Ultrafocused Electromagnetic Field Pulses with a Hollow Cylindrical Waveguide

NASA Astrophysics Data System (ADS)

Maurer, P.; Prat-Camps, J.; Cirac, J. I.; Hänsch, T. W.; Romero-Isart, O.

2017-07-01

We theoretically show that a dipole externally driven by a pulse with a lower-bounded temporal width, and placed inside a cylindrical hollow waveguide, can generate a train of arbitrarily short and focused electromagnetic pulses. The waveguide encloses vacuum with perfect electric conducting walls. A dipole driven by a single short pulse, which is properly engineered to exploit the linear spectral filtering of the cylindrical hollow waveguide, excites longitudinal waveguide modes that are coherently refocused at some particular instances of time, thereby producing arbitrarily short and focused electromagnetic pulses. We numerically show that such ultrafocused pulses persist outside the cylindrical waveguide at distances comparable to its radius.

Personnel electronic neutron dosimeter

DOEpatents

Falk, Roger B.; Tyree, William H.

1984-12-18

A personnel electronic dosimeter includes a neutron-proton and neutron-alpha converter for providing an electrical signal having a magnitude proportional to the energy of a detected proton or alpha particle produced from the converter, a pulse generator circuit for generating a pulse having a duration controlled by the weighed effect of the amplitude of the electrical signal, an oscillator enabled by the pulse for generating a train of clock pulses for a time dependent upon the pulse length, a counter for counting the clock pulses, and an indicator for providing a direct reading and aural alarm when the count indicates that the wearer has been exposed to a selected level of neutron dose equivalent.

Photonic integrated circuit as a picosecond pulse timing discriminator.

PubMed

Lowery, Arthur James; Zhuang, Leimeng

2016-04-18

We report the first experimental demonstration of a compact on-chip optical pulse timing discriminator that is able to provide an output voltage proportional to the relative timing of two 60-ps input pulses on separate paths. The output voltage is intrinsically low-pass-filtered, so the discriminator forms an interface between high-speed optics and low-speed electronics. Potential applications include timing synchronization of multiple pulse trains as a precursor for optical time-division multiplexing, and compact rangefinders with millimeter dimensions.

Dynamic Chirp Control and Pulse Compression for Attosecond High-Order Harmonic Emission

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng Yinghui; Zeng Zhinan; Zou Pu

2009-07-24

We propose a scheme to compensate dynamically the intrinsic chirp of the attosecond harmonic pulses. By adding a weak second harmonic laser field to the driving laser field, the chirp compensation can be varied from the negative to the positive continuously by simply adjusting the relative time delay between the two-color pulses. Using this technique, the compensation of the negative chirp in harmonic emission is demonstrated experimentally for the first time and the nearly transform-limited attosecond pulse trains are obtained.

Shared internal models for feedforward and feedback control.

PubMed

Wagner, Mark J; Smith, Maurice A

2008-10-15

A child often learns to ride a bicycle in the driveway, free of unforeseen obstacles. Yet when she first rides in the street, we hope that if a car suddenly pulls out in front of her, she will combine her innate goal of avoiding an accident with her learned knowledge of the bicycle, and steer away or brake. In general, when we train to perform a new motor task, our learning is most robust if it updates the rules of online error correction to reflect the rules and goals of the new task. Here we provide direct evidence that, after a new feedforward motor adaptation, motor feedback responses to unanticipated errors become precisely task appropriate, even when such errors were never experienced during training. To study this ability, we asked how, if at all, do online responses to occasional, unanticipated force pulses during reaching arm movements change after adapting to altered arm dynamics? Specifically, do they change in a task-appropriate manner? In our task, subjects learned novel velocity-dependent dynamics. However, occasional force-pulse perturbations produced unanticipated changes in velocity. Therefore, after adaptation, task-appropriate responses to unanticipated pulses should compensate corresponding changes in velocity-dependent dynamics. We found that after adaptation, pulse responses precisely compensated these changes, although they were never trained to do so. These results provide evidence for a smart feedback controller which automatically produces responses specific to the learned dynamics of the current task. To accomplish this, the neural processes underlying feedback control must (1) be capable of accurate real-time state prediction for velocity via a forward model and (2) have access to recently learned changes in internal models of limb dynamics.

Alleviation of Pressure Pulse Effects for Trains Entering Tunnels

DOT National Transportation Integrated Search

1979-06-01

This study was carried out for the Transportation Systems Center of the U.S. Department of Transportation on behalf of the Urban Mass Transportation Administration in order to determine to what degree it is possible to attenuate the effects of pressu...

Wide-Range Temperature Sensors with High-Level Pulse Train Output

NASA Technical Reports Server (NTRS)

Hammoud, Ahmad; Patterson, Richard L.

2009-01-01

Two types of temperature sensors have been developed for wide-range temperature applications. The two sensors measure temperature in the range of -190 to +200 C and utilize a thin-film platinum RTD (resistance temperature detector) as the temperature-sensing element. Other parts used in the fabrication of these sensors include NPO (negative-positive- zero) type ceramic capacitors for timing, thermally-stable film or wirewound resistors, and high-temperature circuit boards and solder. The first type of temperature sensor is a relaxation oscillator circuit using an SOI (silicon-on-insulator) operational amplifier as a comparator. The output is a pulse train with a period that is roughly proportional to the temperature being measured. The voltage level of the pulse train is high-level, for example 10 V. The high-level output makes the sensor less sensitive to noise or electromagnetic interference. The output can be read by a frequency or period meter and then converted into a temperature reading. The second type of temperature sensor is made up of various types of multivibrator circuits using an SOI type 555 timer and the passive components mentioned above. Three configurations have been developed that were based on the technique of charging and discharging a capacitor through a resistive element to create a train of pulses governed by the capacitor-resistor time constant. Both types of sensors, which operated successfully over the wide temperature range, have potential use in extreme temperature environments including jet engines and space exploration missions.

Femtosecond optical packet generation by a direct space-to-time pulse shaper.

PubMed

Leaird, D E; Weiner, A M

1999-06-15

We demonstrate femtosecond operation of a direct space-to-time pulse shaper in which there is direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. We use this apparatus to generate trains of 20 pulses as an ultrafast optical data packet over an approximately 40-ps temporal window.

Influence of electron dynamics on the enhancement of double-pulse femtosecond laser-induced breakdown spectroscopy of fused silica

NASA Astrophysics Data System (ADS)

Cao, Zhitao; Jiang, Lan; Wang, Sumei; Wang, Mengmeng; Liu, Lei; Yang, Fan; Lu, Yongfeng

2018-03-01

Femtosecond laser pulse train induced breakdown of fused silica was studied by investigating its plasma emission and the ablated crater morphology. It was demonstrated that the electron dynamics in the ablated fused silica play a dominant role in the emission intensity of induced plasma and the volume of material removal, corresponding to the evolution of free-electron, self-trapped excitons, and the phase change of the fused silica left over by the first pulse. For a fluence of 11 J/cm2, the maximum plasma intensity of double-pulse irradiation at an interpulse delay of 120 ps was about 35 times stronger than that of a single-pulse, while the ablated crater was reduced by 27% in volume. The ionization of slow plume component generated by the first pulse was found to be the main reason for the extremely high intensity enhancement for an interpulse delay of over 10 ps. The results serve as a route to simultaneously increase the spatial resolution and plasma intensity in laser-induced breakdown spectroscopy of dielectrics.

Depth dependent variation of the echolocation pulse rate of bottlenose dolphins (Tursiops truncatus).

PubMed

Simard, Peter; Hibbard, Ashley L; McCallister, Kimberly A; Frankel, Adam S; Zeddies, David G; Sisson, Geoffrey M; Gowans, Shannon; Forys, Elizabeth A; Mann, David A

2010-01-01

Trained odontocetes appear to have good control over the timing (pulse rate) of their echolocation clicks; however, there is comparatively little information about how free-ranging odontocetes modify their echolocation in relation to their environment. This study investigates echolocation pulse rate in 14 groups of free-ranging bottlenose dolphins (Tursiops truncatus) at a variety of depths (2.4-30.1 m) in the Gulf of Mexico. Linear regression models indicated a significant decrease in mean pulse rate with mean water depth. Pulse rates for most groups were multi-modal. Distance to target estimates were as high as 91.8 m, assuming that echolocation was produced at a maximal rate for the target distance. A 5.29-ms processing lag time was necessary to explain the pulse rate modes observed. Although echolocation is likely reverberation limited, these results support the hypotheses that free-ranging bottlenose dolphins in this area are adapting their echolocation signals for a variety of target detection and ranging purposes, and that the target distance is a function of water depth.

Measurement and control of the frequency chirp rate of high-order harmonic pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauritsson, J.; Johnsson, P.; Lopez-Martens, R.

2004-08-01

We measure the chirp rate of harmonics 13 to 23 in argon by cross correlation with a 12 femtosecond probe pulse. Under low ionization conditions, we directly measure the negative chirp due to the atomic dipole phase, and show that an additional chirp on the pump pulse is transferred to the qth harmonic as q times the fundamental chirp. Our results are in accord with simulations using the experimentally measured 815 nm pump and probe pulses. The ability to measure and manipulate the harmonic chirp rate is essential for the characterization and optimization of attosecond pulse trains.

Signal recognition efficiencies of artificial neural-network pulse-shape discrimination in HPGe -decay searches

NASA Astrophysics Data System (ADS)

Caldwell, A.; Cossavella, F.; Majorovits, B.; Palioselitis, D.; Volynets, O.

2015-07-01

A pulse-shape discrimination method based on artificial neural networks was applied to pulses simulated for different background, signal and signal-like interactions inside a germanium detector. The simulated pulses were used to investigate variations of efficiencies as a function of used training set. It is verified that neural networks are well-suited to identify background pulses in true-coaxial high-purity germanium detectors. The systematic uncertainty on the signal recognition efficiency derived using signal-like evaluation samples from calibration measurements is estimated to be 5 %. This uncertainty is due to differences between signal and calibration samples.

Enhancement of the bulbocavernosus reflex during intraoperative neurophysiological monitoring through the use of double train stimulation: a pilot study.

PubMed

Skinner, Stanley; Chiri, Chala A; Wroblewski, Jill; Transfeldt, Ensor E

2007-02-01

Electrophysiological bulbocavernosus reflex (BCR) testing, during surgeries in which the constituent neural components are at risk, might supplement other low sacral (S2-4) stimulation/recording techniques. However, intraoperative BCR is not always reliably implemented. We proposed to analyze BCR signals in five surgical patients monitored with the novel application of double train stimulation (DTS) to determine if the potential could be enhanced. We prospectively planned a regime of DTS BCR with a series of intertrain delays in five monitored patients at risk for low sacral neural injury. Patients were maintained with propofol, opiate infusion, and low inhalant anesthesia without muscle relaxant. Cutaneous sensory nerves of the penis (or clitoris) were stimulated using two consecutive pulse trains (DTS). Intertrain delays were 75, 100, 125, 150, 175, 200, and 250 ms. For BCR recording, uncoated paired wires were inserted into the external anal sphincter (EAS) bilaterally. For each trial, waveform amplitude, duration, and turn count measures for the first (single train) and second (double train) response were recorded. Percent increase/decrease of the second train response compared to the first train response was calculated. There was at least a 30% increase in measures of amplitude, turn count, and duration of the second train response in 22/28, 22/28, and 14/28 of the total trials respectively. There was an insufficient number of independent observations to determine statistical significance. Intraoperative BCR is currently obtained with some difficulty using pulse train stimulation. Our preliminary evidence has identified BCR waveform enhancement using DTS and suggests that the reliability of intraoperative BCR acquisition may be further improved by the addition of this technique. Our data are insufficient to define the best intertrain interval.

Three dimensional cylindrical Kadomtsev-Petviashvili equation in a very dense electron-positron-ion plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

2010-03-15

By using the hydrodynamic equations of ions, Thomas-Fermi electron/positron density distribution, and Poisson equation, a three-dimensional cylindrical Kadomtsev-Petviashvili (CKP) equation is derived for small but finite amplitude ion-acoustic waves. The generalized expansion method is used to analytically solve the CKP equation. New class of solutions admits a train of well-separated bell-shaped periodic pulses is obtained. At certain condition, the latter degenerates to solitary wave solution. The effects of physical parameters on the solitary pulse structures are examined. Furthermore, the energy integral equation is used to study the existence regions of the localized pulses. The present study might be helpful tomore » understand the excitation of nonlinear ion-acoustic waves in a very dense astrophysical objects such as white dwarfs.« less

High Harmonic Radiation Generation and Attosecond pulse generation from Intense Laser-Solid Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Alexander Roy; Krushelnick, Karl

2016-09-08

We have studied ion motion effects in high harmonic generation, including shifts to the harmonics which result in degradation of the attosecond pulse train, and how to mitigate them. We have examined the scaling with intensity of harmonic emission. We have also switched the geometry of the interaction to measure, for the first time, harmonics from a normal incidence interaction. This was performed by using a special parabolic reflector with an on axis hole and is to allow measurements of the attosecond pulses using standard techniques. Here is a summary of the findings: First high harmonic generation in laser-solid interactionsmore » at 10 21 Wcm -2, demonstration of harmonic focusing, study of ion motion effects in high harmonic generation in laser-solid interactions, and demonstration of harmonic amplification.« less

Qualitative analysis of ultra-short optical dissipative solitary pulses in the actively mode-locked semiconductor heterolasers with an external fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Campos Acosta, Joaquin; Moreno Zarate, Pedro; Pons Aglio, Alicia

2011-02-01

An advanced qualitative characterization of simultaneously existing various low-power trains of ultra-short optical pulses with an internal frequency modulation in a distributed laser system based on semiconductor heterostructure is presented. The scheme represents a hybrid cavity consisting of a single-mode heterolaser operating in the active mode-locking regime and an external long single-mode optical fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and linear optical losses. In fact, we consider the trains of optical dissipative solitons, which appear within double balance between the second-order dispersion and cubic-law nonlinearity as well as between the active-medium gain and linear optical losses in a hybrid cavity. Moreover, we operate on specially designed modulating signals providing non-conventional composite regimes of simultaneous multi-pulse active mode-locking. As a result, the mode-locking process allows shaping regular trains of picosecond optical pulses excited by multi-pulse independent on each other sequences of periodic modulations. In so doing, we consider the arranged hybrid cavity as a combination of a quasi-linear part responsible for the active mode-locking by itself and a nonlinear part determining the regime of dissipative soliton propagation. Initially, these parts are analyzed individually, and then the primarily obtained data are coordinated with each other. Within this approach, a contribution of the appeared cubically nonlinear Ginzburg-Landau operator is analyzed via exploiting an approximate variational procedure involving the technique of trial functions.

Interferometer design and controls for pulse stacking in high power fiber lasers

NASA Astrophysics Data System (ADS)

Wilcox, Russell; Yang, Yawei; Dahlen, Dar; Xu, Yilun; Huang, Gang; Qiang, Du; Doolittle, Lawrence; Byrd, John; Leemans, Wim; Ruppe, John; Zhou, Tong; Sheikhsofla, Morteza; Nees, John; Galvanauskas, Almantas; Dawson, Jay; Chen, Diana; Pax, Paul

2017-03-01

In order to develop a design for a laser-plasma accelerator (LPA) driver, we demonstrate key technologies that enable fiber lasers to produce high energy, ultrafast pulses. These technologies must be scalable, and operate in the presence of thermal drift, acoustic noise, and other perturbations typical of an operating system. We show that coherent pulse stacking (CPS), which requires optical interferometers, can be made robust by image-relaying, multipass optical cavities, and by optical phase control schemes that sense pulse train amplitudes from each cavity. A four-stage pulse stacking system using image-relaying cavities is controlled for 14 hours using a pulse-pattern sensing algorithm. For coherent addition of simultaneous ultrafast pulses, we introduce a new scheme using diffractive optics, and show experimentally that four pulses can be added while a preserving pulse width of 128 fs.

Spatial hearing benefits demonstrated with presentation of acoustic temporal fine structure cues in bilateral cochlear implant listeners.

PubMed

Churchill, Tyler H; Kan, Alan; Goupell, Matthew J; Litovsky, Ruth Y

2014-09-01

Most contemporary cochlear implant (CI) processing strategies discard acoustic temporal fine structure (TFS) information, and this may contribute to the observed deficits in bilateral CI listeners' ability to localize sounds when compared to normal hearing listeners. Additionally, for best speech envelope representation, most contemporary speech processing strategies use high-rate carriers (≥900 Hz) that exceed the limit for interaural pulse timing to provide useful binaural information. Many bilateral CI listeners are sensitive to interaural time differences (ITDs) in low-rate (<300 Hz) constant-amplitude pulse trains. This study explored the trade-off between superior speech temporal envelope representation with high-rate carriers and binaural pulse timing sensitivity with low-rate carriers. The effects of carrier pulse rate and pulse timing on ITD discrimination, ITD lateralization, and speech recognition in quiet were examined in eight bilateral CI listeners. Stimuli consisted of speech tokens processed at different electrical stimulation rates, and pulse timings that either preserved or did not preserve acoustic TFS cues. Results showed that CI listeners were able to use low-rate pulse timing cues derived from acoustic TFS when presented redundantly on multiple electrodes for ITD discrimination and lateralization of speech stimuli.

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser.

PubMed

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-19

Dual-comb lasers simultaneously generating asynchronous ultrashort pulses could be an intriguing alternative to the current dual-laser comb source. When generated through a common light path, the low common-mode noises and good coherence between the pulse trains could be realized. Here we demonstrate the completely common-path, unidirectional dual-comb lasing using a carbon nanotube saturable absorber with additional pulse narrowing and broadening mechanisms. The interactions between multiple soliton formation mechanisms result in bifurcation into unusual two-pulse states with pulses of four-fold bandwidth difference and tens-of-Hz repetition rate difference. Coherence between the pulses is verified by the asynchronous cross-sampling and dual-comb spectroscopy measurements.

Peak expiratory flow as a predictor for the effectiveness of sport for patients with COPD.

PubMed

Jungblut, S; Frickmann, H; Klingler, J; Zimmermann, B; Bargon, Joachim

2006-01-31

This study intended to find simple parameters that were able to determine the increase in physical performance as a result of sport in a group of patients with COPD (lung sport). We regularly investigated pulse, oxygenation and peak expiratory flow in participants with COPD of a "lung sport group", who participated in a structured weekly training program under professional supervision. Ten volunteers (7 females, 3 males, median of age = 69) with COPD (grade II-III) took part in the study. - The relative changes after 3 and 6 months were compared with the values of the first month of exercise. Measurements were carried out before exercise, after stamina training and at the end of the program. - Pulse and oxygenation did not show any changes. However, there was a significant improvement of peak flow after 6 months. - These peak flow changes represent further evidence of positive effects of sport in COPD and provide a parameter which allows the patients themselves to measure and evaluate the success of their physical activity.

Amplification of Dynamic Nuclear Polarization at 200 GHz by Arbitrary Pulse Shaping of the Electron Spin Saturation Profile.

PubMed

Kaminker, Ilia; Han, Songi

2018-06-07

Dynamic nuclear polarization (DNP) takes center stage in nuclear magnetic resonance (NMR) as a tool to amplify its signal by orders of magnitude through the transfer of polarization from electron to nuclear spins. In contrast to modern NMR and electron paramagnetic resonance (EPR) that extensively rely on pulses for spin manipulation in the time domain, the current mainstream DNP technology exclusively relies on monochromatic continuous wave (CW) irradiation. This study introduces arbitrary phase shaped pulses that constitute a train of coherent chirp pulses in the time domain at 200 GHz (7 T) to dramatically enhance the saturation bandwidth and DNP performance compared to CW DNP, yielding up to 500-fold in NMR signal enhancements. The observed improvement is attributed to the recruitment of additional electron spins contributing to DNP via the cross-effect mechanism, as experimentally confirmed by two-frequency pump-probe electron-electron double resonance (ELDOR).

Preference pulses and the win-stay, fix-and-sample model of choice.

PubMed

Hachiga, Yosuke; Sakagami, Takayuki; Silberberg, Alan

2015-11-01

Two groups of six rats each were trained to respond to two levers for a food reinforcer. One group was trained on concurrent variable-ratio 20 extinction schedules of reinforcement. The second group was trained on a concurrent variable-interval 27-s extinction schedule. In both groups, lever-schedule assignments changed randomly following reinforcement; a light cued the lever providing the next reinforcer. In the next condition, the light cue was removed and reinforcer assignment strictly alternated between levers. The next two conditions redetermined, in order, the first two conditions. Preference pulses, defined as a tendency for relative response rate to decline to the just-reinforced alternative with time since reinforcement, only appeared during the extinction schedule. Although the pulse's functional form was well described by a reinforcer-induction equation, there was a large residual between actual data and a pulse-as-artifact simulation (McLean, Grace, Pitts, & Hughes, 2014) used to discern reinforcer-dependent contributions to pulsing. However, if that simulation was modified to include a win-stay tendency (a propensity to stay on the just-reinforced alternative), the residual was greatly reduced. Additional modifications of the parameter values of the pulse-as-artifact simulation enabled it to accommodate the present results as well as those it originally accommodated. In its revised form, this simulation was used to create a model that describes response runs to the preferred alternative as terminating probabilistically, and runs to the unpreferred alternative as punctate with occasional perseverative response runs. After reinforcement, choices are modeled as returning briefly to the lever location that had been just reinforced. This win-stay propensity is hypothesized as due to reinforcer induction. © Society for the Experimental Analysis of Behavior.

All solid-state high power microwave source with high repetition frequency.

PubMed

Bragg, J-W B; Sullivan, W W; Mauch, D; Neuber, A A; Dickens, J C

2013-05-01

An all solid-state, megawatt-class high power microwave system featuring a silicon carbide (SiC) photoconductive semiconductor switch (PCSS) and a ferrimagnetic-based, coaxial nonlinear transmission line (NLTL) is presented. A 1.62 cm(2), 50 kV 4H-SiC PCSS is hard-switched to produce electrical pulses with 7 ns full width-half max (FWHM) pulse widths at 2 ns risetimes in single shot and burst-mode operation. The PCSS resistance drops to sub-ohm when illuminated with approximately 3 mJ of laser energy at 355 nm (tripled Nd:YAG) in a single pulse. Utilizing a fiber optic based optical delivery system, a laser pulse train of four 7 ns (FWHM) signals was generated at 65 MHz repetition frequency. The resulting electrical pulse train from the PCSS closely follows the optical input and is utilized to feed the NLTL generating microwave pulses with a base microwave-frequency of about 2.1 GHz at 65 MHz pulse repetition frequency (prf). Under typical experimental conditions, the NLTL produces sharpened output risetimes of 120 ps and microwave oscillations at 2-4 GHz that are generated due to damped gyromagnetic precession of the ferrimagnetic material's axially pre-biased magnetic moments. The complete system is discussed in detail with its output matched into 50 Ω, and results covering MHz-prf in burst-mode operation as well as frequency agility in single shot operation are discussed.

Directing Nuclear Spin Flips in InAs Quantum Dots Using Detuned Optical Pulse Trains

DTIC Science & Technology

2009-04-24

Directing Nuclear Spin Flips in InAs Quantum Dots Using Detuned Optical Pulse Trains S . G. Carter,1 A. Shabaev,2 Sophia E. Economou,1 T. A. Kennedy,1...A. S . Bracker,1 and T. L. Reinecke1 1Naval Research Laboratory, Washington, D.C. 20375-5322, USA 2School of Computational Sciences, George Mason...trion spin states and the allowed transitions. Single (double) arrows are electron (hole) spins. PRL 102, 167403 (2009) P HY S I CA L R EV I EW LE T T ER

Apparatus for millimeter-wave signal generation

DOEpatents

Vawter, G. Allen; Hietala, Vincent M.; Zolper, John C.; Mar, Alan; Hohimer, John P.

1999-01-01

An opto-electronic integrated circuit (OEIC) apparatus is disclosed for generating an electrical signal at a frequency .gtoreq.10 GHz. The apparatus, formed on a single substrate, includes a semiconductor ring laser for generating a continuous train of mode-locked lasing pulses and a high-speed photodetector for detecting the train of lasing pulses and generating the electrical signal therefrom. Embodiments of the invention are disclosed with an active waveguide amplifier coupling the semiconductor ring laser and the high-speed photodetector. The invention has applications for use in OEICs and millimeter-wave monolithic integrated circuits (MMICs).

Remote distribution of a mode-locked pulse train with sub 40-as jitter

NASA Astrophysics Data System (ADS)

Chen, Yi-Fei; Jiang, Jie; Jones, David J.

2006-12-01

Remote transfer of an ultralow-jitter microwave frequency reference signal is demonstrated using the pulse trains generated by a mode-locked fiber laser. The timing jitter in a ~ 30-m fiber link is reduced to 38 attoseconds (as) integrated over a bandwidth from 1 Hz to 10 MHz via active stabilization which represents a significant improvement over previously reported jitter performance. Our approach uses an all-optical generation of the synchronization error signal and an accompanying out-of-loop optical detection technique to verify the jitter performance.

Postnatal development of echolocation abilities in a bottlenose dolphin (Tursiops truncatus): temporal organization.

PubMed

Favaro, Livio; Gnone, Guido; Pessani, Daniela

2013-03-01

In spite of all the information available on adult bottlenose dolphin (Tursiops truncatus) biosonar, the ontogeny of its echolocation abilities has been investigated very little. Earlier studies have reported that neonatal dolphins can produce both whistles and burst-pulsed sounds just after birth and that early-pulsed sounds are probably a precursor of echolocation click trains. The aim of this research is to investigate the development of echolocation signals in a captive calf, born in the facilities of the Acquario di Genova. A set of 81 impulsive sounds were collected from birth to the seventh postnatal week and six additional echolocation click trains were recorded when the dolphin was 1 year old. Moreover, behavioral observations, concurring with sound production, were carried out by means of a video camera. For each sound we measured five acoustic parameters: click train duration (CTD), number of clicks per train, minimum, maximum, and mean click repetition rate (CRR). CTD and number of clicks per train were found to increase with age. Maximum and mean CRR followed a decreasing trend with dolphin growth starting from the second postnatal week. The calf's first head scanning movement was recorded 21 days after birth. Our data suggest that in the bottlenose dolphin the early postnatal weeks are essential for the development of echolocation abilities and that the temporal features of the echolocation click trains remain relatively stable from the seventh postnatal week up to the first year of life. © 2013 Wiley Periodicals, Inc.

When to Stop CPR and When to Perform Rhythm Analysis: Potential Confusion Among ACLS Providers.

PubMed

Giberson, Brandon; Uber, Amy; F Gaieski, David; Miller, Joseph B; Wira, Charles; Berg, Katherine; Giberson, Tyler; Cocchi, Michael N; S Abella, Benjamin; Donnino, Michael W

2016-09-01

Health care providers nationwide are routinely trained in Advanced Cardiac Life Support (ACLS), an American Heart Association program that teaches cardiac arrest management. Recent changes in the ACLS approach have de-emphasized routine pulse checks in an effort to promote uninterrupted chest compressions. We hypothesized that this new ACLS algorithm may lead to uncertainty regarding the appropriate action following detection of a pulse during a cardiac arrest. We conducted an observational study in which a Web-based survey was sent to ACLS-trained medical providers at 4 major urban tertiary care centers in the United States. The survey consisted of 5 multiple-choice, scenario-based ACLS questions, including our question of interest. Adult staff members with a valid ACLS certification were included. A total of 347 surveys were analyzed. The response rate was 28.1%. The majority (53.6%) of responders were between 18 and 32 years old, and 59.9% were female. The majority (54.2%) of responders incorrectly stated that they would continue CPR and possibly administer additional therapies when a team member detects a pulse immediately following defibrillation. Secondarily, only 51.9% of respondents correctly chose to perform a rhythm check following 2 minutes of CPR. The other 3 survey questions were correctly answered an average of 89.1% of the time. Confusion exists regarding whether or not CPR and cardiac medications should be continued in the presence of a pulse. Education may be warranted to emphasize avoiding compressions and medications when a palpable pulse is detected. © The Author(s) 2014.

Increasing sensitivity of pulse EPR experiments using echo train detection schemes.

PubMed

Mentink-Vigier, F; Collauto, A; Feintuch, A; Kaminker, I; Tarle, V; Goldfarb, D

2013-11-01

Modern pulse EPR experiments are routinely used to study the structural features of paramagnetic centers. They are usually performed at low temperatures, where relaxation times are long and polarization is high, to achieve a sufficient Signal/Noise Ratio (SNR). However, when working with samples whose amount and/or concentration are limited, sensitivity becomes an issue and therefore measurements may require a significant accumulation time, up to 12h or more. As the detection scheme of practically all pulse EPR sequences is based on the integration of a spin echo--either primary, stimulated or refocused--a considerable increase in SNR can be obtained by replacing the single echo detection scheme by a train of echoes. All these echoes, generated by Carr-Purcell type sequences, are integrated and summed together to improve the SNR. This scheme is commonly used in NMR and here we demonstrate its applicability to a number of frequently used pulse EPR experiments: Echo-Detected EPR, Davies and Mims ENDOR (Electron-Nuclear Double Resonance), DEER (Electron-Electron Double Resonance|) and EDNMR (Electron-Electron Double Resonance (ELDOR)-Detected NMR), which were combined with a Carr-Purcell-Meiboom-Gill (CPMG) type detection scheme at W-band. By collecting the transient signal and integrating a number of refocused echoes, this detection scheme yielded a 1.6-5 folds SNR improvement, depending on the paramagnetic center and the pulse sequence applied. This improvement is achieved while keeping the experimental time constant and it does not introduce signal distortion. Copyright © 2013 Elsevier Inc. All rights reserved.

Femtosecond direct space-to-time pulse shaping in an integrated-optic configuration.

PubMed

Leaird, D E; Weiner, A M

2004-07-01

We demonstrate femtosecond operation of an integrated-optic direct space-to-time pulse shaper for which there is a direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. The apparatus is used to generate trains of more than 30 pulses as an ultrafast optical data packet over approximately an 80-ps temporal window.

One-dimensional "atom" with zero-range potential perturbed by finite sequence of zero-duration laser pulses

NASA Astrophysics Data System (ADS)

Gusev, A. A.; Chuluunbaatar, O.; Popov, Yu. V.; Vinitsky, S. I.; Derbov, V. L.; Lovetskiy, K. P.

2018-04-01

The exactly soluble model of a train of zero-duration electromagnetic pulses interacting with a 1D atom with short-range interaction potential modelled by a δ-function is considered. The model is related to the up-to-date laser techniques providing the duration of pulses as short as a few attoseconds and the intensities higher than 1014 W/cm2.

Imperfect pitch: Gabor's uncertainty principle and the pitch of extremely brief sounds.

PubMed

Hsieh, I-Hui; Saberi, Kourosh

2016-02-01

How brief must a sound be before its pitch is no longer perceived? The uncertainty tradeoff between temporal and spectral resolution (Gabor's principle) limits the minimum duration required for accurate pitch identification or discrimination. Prior studies have reported that pitch can be extracted from sinusoidal pulses as brief as half a cycle. This finding has been used in a number of classic papers to develop models of pitch encoding. We have found that phase randomization, which eliminates timbre confounds, degrades this ability to chance, raising serious concerns over the foundation on which classic pitch models have been built. The current study investigated whether subthreshold pitch cues may still exist in partial-cycle pulses revealed through statistical integration in a time series containing multiple pulses. To this end, we measured frequency-discrimination thresholds in a two-interval forced-choice task for trains of partial-cycle random-phase tone pulses. We found that residual pitch cues exist in these pulses but discriminating them requires an order of magnitude (ten times) larger frequency difference than that reported previously, necessitating a re-evaluation of pitch models built on earlier findings. We also found that as pulse duration is decreased to less than two cycles its pitch becomes biased toward higher frequencies, consistent with predictions of an auto-correlation model of pitch extraction.

Optimization of identity operation in NMR spectroscopy via genetic algorithm: Application to the TEDOR experiment

NASA Astrophysics Data System (ADS)

Manu, V. S.; Veglia, Gianluigi

2016-12-01

Identity operation in the form of π pulses is widely used in NMR spectroscopy. For an isolated single spin system, a sequence of even number of π pulses performs an identity operation, leaving the spin state essentially unaltered. For multi-spin systems, trains of π pulses with appropriate phases and time delays modulate the spin Hamiltonian to perform operations such as decoupling and recoupling. However, experimental imperfections often jeopardize the outcome, leading to severe losses in sensitivity. Here, we demonstrate that a newly designed Genetic Algorithm (GA) is able to optimize a train of π pulses, resulting in a robust identity operation. As proof-of-concept, we optimized the recoupling sequence in the transferred-echo double-resonance (TEDOR) pulse sequence, a key experiment in biological magic angle spinning (MAS) solid-state NMR for measuring multiple carbon-nitrogen distances. The GA modified TEDOR (GMO-TEDOR) experiment with improved recoupling efficiency results in a net gain of sensitivity up to 28% as tested on a uniformly 13C, 15N labeled microcrystalline ubiquitin sample. The robust identity operation achieved via GA paves the way for the optimization of several other pulse sequences used for both solid- and liquid-state NMR used for decoupling, recoupling, and relaxation experiments.

HAL® exoskeleton training improves walking parameters and normalizes cortical excitability in primary somatosensory cortex in spinal cord injury patients.

PubMed

Sczesny-Kaiser, Matthias; Höffken, Oliver; Aach, Mirko; Cruciger, Oliver; Grasmücke, Dennis; Meindl, Renate; Schildhauer, Thomas A; Schwenkreis, Peter; Tegenthoff, Martin

2015-08-20

Reorganization in the sensorimotor cortex accompanied by increased excitability and enlarged body representations is a consequence of spinal cord injury (SCI). Robotic-assisted bodyweight supported treadmill training (BWSTT) was hypothesized to induce reorganization and improve walking function. To assess whether BWSTT with hybrid assistive limb® (HAL®) exoskeleton affects cortical excitability in the primary somatosensory cortex (S1) in SCI patients, as measured by paired-pulse somatosensory evoked potentials (ppSEP) stimulated above the level of injury. Eleven SCI patients took part in HAL® assisted BWSTT for 3 months. PpSEP were conducted before and after this training period, where the amplitude ratios (SEP amplitude following double pulses - SEP amplitude following single pulses) were assessed and compared to eleven healthy control subjects. To assess improvement in walking function, we used the 10-m walk test, timed-up-and-go test, the 6-min walk test, and the lower extremity motor score. PpSEPs were significantly increased in SCI patients as compared to controls at baseline. Following training, ppSEPs were increased from baseline and no longer significantly differed from controls. Walking parameters also showed significant improvements, yet there was no significant correlation between ppSEP measures and walking parameters. The findings suggest that robotic-assisted BWSTT with HAL® in SCI patients is capable of inducing cortical plasticity following highly repetitive, active locomotive use of paretic legs. While there was no significant correlation of excitability with walking parameters, brain areas other than S1 might reflect improvement of walking functions. EEG and neuroimaging studies may provide further information about supraspinal plastic processes and foci in SCI rehabilitation.

An investigation of fatigue phenomenon in the upper limb muscle due to short duration pulses in an FES system

NASA Astrophysics Data System (ADS)

Naeem, Jannatul; Wong Azman, Amelia; Khan, Sheroz; Mohd Mustafah, Yasir

2013-12-01

Functional Electrical Stimulation (FES) is a method of artificially stimulating muscles or nerves in order to result in contraction or relaxation of muscles. Many studies have shown that FES system has helped patients to live a better lives especially those who are suffering from physical mobility. Unfortunately, one of the main limitations of an FES system besides of its high cost is largely due to muscle fatigue. Muscle fatigue will affect the training duration which could delay patients' recovery rate. In this paper, we analyzed the occurrence of this fatigue phenomenon in terms of stimulator parameters such as amplitude, frequency, pulse width and pulse shape. The objective of this investigation is to identify other key features of the FES system parameters in order to prolong the training duration among patients. The experiment has been done on a healthy person for the duration of one minute and later the muscles response will be observed. Resultant muscle response is recorded as force using force resistive sensor. The experimental results show muscles will get fatigue at a different rate as the frequency increases. The experiment also shows that the duty cycle is reciprocal to the resultant force.

Benefits of cardiac sonography performed by a non-expert sonographer in patients with non-traumatic cardiopulmonary arrest.

PubMed

Zengin, Suat; Yavuz, Erdal; Al, Behçet; Cindoruk, Şener; Altunbaş, Gökhan; Gümüşboğa, Hasan; Yıldırım, Cuma

2016-05-01

The purpose of this study was to evaluate a rapid cardiac ultrasound assessment performed by trained non-expert sonographers integrated into the advanced cardiac life support (ACLS). This study was prospectively performed in 179 patients (104 males and 75 females) who underwent cardiopulmonary resuscitation (CPR) in an emergency department (ED) during two calendar years (2013 and 2014). Two senior doctors, who had received emergency cardiac ultrasonography training, performed cardiac ultrasound through the apical, subxiphoid, or parasternal windows. Ultrasound evaluation and pulse controls were performed simultaneously. SPSS 18.0 was used for statistical analysis. A total of 63.7% (114) of the cardiopulmonary arrest incidents occurred out of the hospital. Only 13 patients had a femoral pulse during the initial evaluation, while 166 showed no femoral pulse. Initial monitoring showed a regular rhythm in 53 patients, ventricular fibrillation in 18 patients, and no rhythms in 108 patients. The first evaluation with ultrasound detected an effective heart rate in 26 patients and ventricular fibrillation in 14 patients, while no effective heart rate was observed in 139 patients. In addition, ultrasound revealed pericardial tamponade in seven patients and right ventricular enlargement in four cases. Global hypokinesia was detected in four patients and hypovolemia was observed in another four patients. The use of real-time ultrasonography during resuscitation with real-time femoral pulse check can help facilitate the distinguishing of pea-type arrest, ascertain the cause of the arrest, infer a suitable treatment, and optimize medical management decisions regarding CPR termination. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

1030-nm diode-laser-based light source delivering pulses with nanojoule energies and picosecond duration adjustable by mode locking or pulse gating operation

NASA Astrophysics Data System (ADS)

Klehr, A.; Liero, A.; Wenzel, H.; Bugge, F.; Brox, O.; Fricke, J.; Ressel, P.; Knigge, A.; Heinrich, W.; Tränkle, G.

2017-02-01

A new compact 1030 nm picosecond light source which can be switched between pulse gating and mode locking operation is presented. It consists of a multi-section distributed Bragg reflector (DBR) laser, an ultrafast multisection optical gate and a flared power amplifier (PA), mounted together with high frequency electronics and optical elements on a 5×4 cm micro bench. The master oscillator (MO) is a 10 mm long ridge wave-guide (RW) laser consisting of 200 μm long saturable absorber, 1500 μm long gain, 8000 μm long cavity, 200 μm long DBR and 100 μm long monitor sections. The 2 mm long optical gate consisting of several RW sections is monolithically integrated with the 4 mm long gain-guided tapered amplifier on a single chip. The light source can be switched between pulse gating and passive mode locking operation. For pulse gating all sections of the MO (except of the DBR and monitor sections) are forward biased and driven by a constant current. By injecting electrical pulses into one section of the optical gate the CW beam emitted by the MO is converted into a train of optical pulses with adjustable widths between 250 ps and 1000 ps. Peak powers of 20 W and spectral linewidths in the MHz range are achieved. Shorter pulses with widths between 4 ps and 15 ps and peak powers up to 50 W but larger spectral widths of about 300 pm are generated by mode locking where the saturable absorber section of the MO is reversed biased. The repetition rate of 4.2 GHz of the pulse train emitted by the MO can be reduced to values between 1 kHz and 100 MHz by utilizing the optical gate as pulse picker. The pulse-to-pulse distance can be controlled by an external trigger source.

Mode-locked laser with pulse interleavers in a monolithic photonic integrated circuit for millimeter wave and terahertz carrier generation.

PubMed

Lo, Mu-Chieh; Guzmán, Robinson; Gordón, Carlos; Carpintero, Guillermo

2017-04-15

This Letter presents a photonics-based millimeter wave and terahertz frequency synthesizer using a monolithic InP photonic integrated circuit composed of a mode-locked laser (MLL) and two pulse interleaver stages to multiply the repetition rate frequency. The MLL is a multiple colliding pulse MLL producing an 80 GHz repetition rate pulse train. Through two consecutive monolithic pulse interleaver structures, each doubling the repetition rate, we demonstrate the achievement of 160 and 320 GHz. The fabrication was done on a multi-project wafer run of a generic InP photonic technology platform.

Simulation of Rate-Related (Dead-Time) Losses In Passive Neutron Multiplicity Counting Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, L.G.; Norman, P.I.; Leadbeater, T.W.

Passive Neutron Multiplicity Counting (PNMC) based on Multiplicity Shift Register (MSR) electronics (a form of time correlation analysis) is a widely used non-destructive assay technique for quantifying spontaneously fissile materials such as Pu. At high event rates, dead-time losses perturb the count rates with the Singles, Doubles and Triples being increasingly affected. Without correction these perturbations are a major source of inaccuracy in the measured count rates and assay values derived from them. This paper presents the simulation of dead-time losses and investigates the effect of applying different dead-time models on the observed MSR data. Monte Carlo methods have beenmore » used to simulate neutron pulse trains for a variety of source intensities and with ideal detection geometry, providing an event by event record of the time distribution of neutron captures within the detection system. The action of the MSR electronics was modelled in software to analyse these pulse trains. Stored pulse trains were perturbed in software to apply the effects of dead-time according to the chosen physical process; for example, the ideal paralysable (extending) and non-paralysable models with an arbitrary dead-time parameter. Results of the simulations demonstrate the change in the observed MSR data when the system dead-time parameter is varied. In addition, the paralysable and non-paralysable models of deadtime are compared. These results form part of a larger study to evaluate existing dead-time corrections and to extend their application to correlated sources. (authors)« less

Intermittent, moderate-intensity aerobic exercise for only eight weeks reduces arterial stiffness: evaluation by measurement of stiffness parameter and pressure-strain elastic modulus by use of ultrasonic echo tracking.

PubMed

Tanaka, Midori; Sugawara, Motoaki; Ogasawara, Yasuo; Izumi, Tadafumi; Niki, Kiyomi; Kajiya, Fumihiko

2013-04-01

Aerobic exercise has been reported to be associated with reduced arterial stiffness. However, the intensity, duration, and frequency of aerobic exercise required to improve arterial stiffness have not been established. In addition, most reports base their conclusions on changes in pulse wave velocity, which is an indirect index of arterial stiffness. We studied the effects of short-term, intermittent, moderate-intensity exercise training on arterial stiffness based on measurements of the stiffness parameter (β) and pressure-strain elastic modulus (E p), which are direct indices of regional arterial stiffness. A total of 25 young healthy volunteers (18 men) were recruited. By use of ultrasonic diagnostic equipment we measured β and E p of the carotid artery before and after 8 weeks of exercise training. After exercise training, systolic pressure (P s), diastolic pressure (P d), pulse pressure, systolic arterial diameter (D s), and diastolic arterial diameter (D d) did not change significantly. However, the pulsatile change in diameter ((D s - D d)/D d) increased significantly, and β and E p decreased significantly. For healthy young subjects, β and E p were reduced by intermittent, moderate-intensity exercise training for only 8 weeks.

Possible Evidence for an Event Horizon in Cyg XR-1

NASA Technical Reports Server (NTRS)

Dolan, Joseph F.; Fisher, Richard R. (Technical Monitor)

2001-01-01

The X-ray emitting component in the Cyg XR-1/HDE226868 system is a leading candidate for identification as a stellar-mass sized black hole. The positive identification of a black hole as predicted by general relativity requires the detection of an event horizon surrounding the point singularity. One signature of such an event horizon would be the existence of dying pulse trains emitted by material spiraling into the event horizon from the last stable orbit around the black hole. We observed the Cyg XR-1 system at three different epochs in a 1400 - 3000 A bandpass with 0.1 ms time resolution using the Hubble Space Telescope's High Speed Photometer. Repeated excursions of the detected flux by more than three standard deviations above the mean are present in the UV flux with FWHM 1 - 10 ms. If any of these excursions are pulses of radiation produced in the system (and not just stochastic variability associated with the Poisson distribution of detected photon arrival times), then this short a timescale requires that the pulses originate in the accretion disk around Cyg XR-1. Two series of pulses with characteristics similar to those expected from dying pulse trains were detected in three hours of observation.

Evolution of Hyperbolic-Secant Pulses Towards Cross-Phase Modulation Induced Optical Wave Breaking and Soliton or Soliton Trains Generation in Quintic Nonlinear Fibers

NASA Astrophysics Data System (ADS)

Zhong, Xian-Qiong; Zhang, Xiao-Xia; Du, Xian-Tong; Liu, Yong; Cheng, Ke

2015-10-01

The approximate analytical frequency chirps and the critical distances for cross-phase modulation induced optical wave breaking (OWB) of the initial hyperbolic-secant optical pulses propagating in optical fibers with quintic nonlinearity (QN) are presented. The pulse evolutions in terms of the frequency chirps, shapes and spectra are numerically calculated in the normal dispersion regime. The results reveal that, depending on different QN parameters, the traditional OWB or soliton or soliton pulse trains may occur. The approximate analytical critical distances are found to be in good agreement with the numerical ones only for the traditional OWB whereas the approximate analytical frequency chirps accords well with the numerical ones at the initial evolution stages of the pulses. Supported by the Postdoctoral Fund of China under Grant No. 2011M501402, the Key Project of Chinese Ministry of Education under Grant No. 210186, the Major Project of Natural Science Supported by the Educational Department of Sichuan Province under Grant No. 13ZA0081, the Key Project of National Natural Science Foundation of China under Grant No 61435010, and the National Natural Science Foundation of China under Grant No. 61275039

Implementing a Digital Phasemeter in an FPGA

NASA Technical Reports Server (NTRS)

Rao, Shanti R.

2008-01-01

Firmware for implementing a digital phasemeter within a field-programmable gate array (FPGA) has been devised. In the original application of this firmware, the phase that one seeks to measure is the difference between the phases of two nominally-equal-frequency heterodyne signals generated by two interferometers. In that application, zero-crossing detectors convert the heterodyne signals to trains of rectangular pulses, the two pulse trains are fed to a fringe counter (the major part of the phasemeter) controlled by a clock signal having a frequency greater than the heterodyne frequency, and the fringe counter computes a time-averaged estimate of the difference between the phases of the two pulse trains. The firmware also does the following: Causes the FPGA to compute the frequencies of the input signals; Causes the FPGA to implement an Ethernet (or equivalent) transmitter for readout of phase and frequency values; and Provides data for use in diagnosis of communication failures. The readout rate can be set, by programming, to a value between 250 Hz and 1 kHz. Network addresses can be programmed by the user.

Linear induction accelerator and pulse forming networks therefor

DOEpatents

Buttram, Malcolm T.; Ginn, Jerry W.

1989-01-01

A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities.

Multiple polarization states of vector soliton in fiber laser

NASA Astrophysics Data System (ADS)

Chen, Weicheng; Xu, Wencheng; Cao, Hui; Han, Dingan

2007-11-01

Vector soliton is obtained in erbium-doped fiber laser via nonlinear polarization rotation techniques. In experiment, we observe the every 4- and 7-pulse sinusoidal peak modulation. Temporal pulse sinusoidal peak modulation owes to evolution behavior of vector solitons in multiple polarization states. The polarizer in the laser modulates the mode-locked pulses with different polarization states into periodical pulse train intensities modulation. Moreover, the increasing pumping power lead to the appearance of the harmonic pulses and change the equivalent beat length to accelerate the polarization rotation. When the laser cavity length is the n-th multiple ratios to the beat length to maintain the mode-locking, the mode-locked vector soliton is in n-th multiple polarization states, exhibiting every n-pulse sinusoidal peak modulation.

Conditioned Side Effects Induced by Cancer Chemotherapy: Prevention Through Behavioral Treatment.

ERIC Educational Resources Information Center

Burish, Thomas G.; And Others

1987-01-01

Studied cancer patients (N=24) in order to determine whether conditioned nausea and vomiting could be delayed or prevented. Indicated that patients receiving progressive muscle relaxation training and guided imagery had significantly less nausea and vomiting and significanty lower blood pressures, pulse rates, and dysphoria, especially anxiety,…

A novel fiber laser development for photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Yavas, Seydi; Aytac-Kipergil, Esra; Arabul, Mustafa U.; Erkol, Hakan; Akcaalan, Onder; Eldeniz, Y. Burak; Ilday, F. Omer; Unlu, Mehmet B.

2013-03-01

Photoacoustic microscopy, as an imaging modality, has shown promising results in imaging angiogenesis and cutaneous malignancies like melanoma, revealing systemic diseases including diabetes, hypertension, tracing drug efficiency and assessment of therapy, monitoring healing processes such as wound cicatrization, brain imaging and mapping. Clinically, photoacoustic microscopy is emerging as a capable diagnostic tool. Parameters of lasers used in photoacoustic microscopy, particularly, pulse duration, energy, pulse repetition frequency, and pulse-to-pulse stability affect signal amplitude and quality, data acquisition speed and indirectly, spatial resolution. Lasers used in photoacoustic microscopy are typically Q-switched lasers, low-power laser diodes, and recently, fiber lasers. Significantly, the key parameters cannot be adjusted independently of each other, whereas microvasculature and cellular imaging, e.g., have different requirements. Here, we report an integrated fiber laser system producing nanosecond pulses, covering the spectrum from 600 nm to 1100 nm, developed specifically for photoacoustic excitation. The system comprises of Yb-doped fiber oscillator and amplifier, an acousto-optic modulator and a photonic-crystal fiber to generate supercontinuum. Complete control over the pulse train, including generation of non-uniform pulse trains, is achieved via the AOM through custom-developed field-programmable gate-array electronics. The system is unique in that all the important parameters are adjustable: pulse duration in the range of 1-3 ns, pulse energy up to 10 μJ, repetition rate from 50 kHz to 3 MHz. Different photocoustic imaging probes can be excited with the ultrabroad spectrum. The entire system is fiber-integrated; guided-beam-propagation rendersit misalignment free and largely immune to mechanical perturbations. The laser is robust, low-cost and built using readily available components.

Pulsing blue light through closed eyelids: effects on acute melatonin suppression and phase shifting of dim light melatonin onset.

PubMed

Figueiro, Mariana G; Plitnick, Barbara; Rea, Mark S

2014-01-01

Circadian rhythm disturbances parallel the increased prevalence of sleep disorders in older adults. Light therapies that specifically target regulation of the circadian system in principle could be used to treat sleep disorders in this population. Current recommendations for light treatment require the patients to sit in front of a bright light box for at least 1 hour daily, perhaps limiting their willingness to comply. Light applied through closed eyelids during sleep might not only be efficacious for changing circadian phase but also lead to better compliance because patients would receive light treatment while sleeping. Reported here are the results of two studies investigating the impact of a train of 480 nm (blue) light pulses presented to the retina through closed eyelids on melatonin suppression (laboratory study) and on delaying circadian phase (field study). Both studies employed a sleep mask that provided narrowband blue light pulses of 2-second duration every 30 seconds from arrays of light-emitting diodes. The results of the laboratory study demonstrated that the blue light pulses significantly suppressed melatonin by an amount similar to that previously shown in the same protocol at half the frequency (ie, one 2-second pulse every minute for 1 hour). The results of the field study demonstrated that blue light pulses given early in the sleep episode significantly delayed circadian phase in older adults; these results are the first to demonstrate the efficacy and practicality of light treatment by a sleep mask aimed at adjusting circadian phase in a home setting.

Attosecond control of orbital parity mix interferences and the relative phase of even and odd harmonics in an attosecond pulse train.

PubMed

Laurent, G; Cao, W; Li, H; Wang, Z; Ben-Itzhak, I; Cocke, C L

2012-08-24

We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train.

Investigating the intersystem crossing rate and triplet quantum yield of Protoporphyrin IX by means of pulse train fluorescence technique

NASA Astrophysics Data System (ADS)

Gotardo, Fernando; Cocca, Leandro H. Z.; Acunha, Thiago V.; Longoni, Ana; Toldo, Josene; Gonçalves, Paulo F. B.; Iglesias, Bernardo A.; De Boni, Leonardo

2017-04-01

Photophysical investigations of PPIX were described in order to determine the triplet conversion efficiency. Time resolved fluorescence and pulse train fluorescence were employed to characterize the main mechanism responsible for deactivation of the first singlet excited state (excited singlet and triplet states). Single pulse and Z-Scan analysis were employed to measure the singlet excited state absorption cross-sections. Theoretical calculations were performed in order to get some properties of PPIX in ground state, first singlet and triplet excited state. A TD-DFT result shows a great possibility of ISC associated to out-of-plane distortions in porphyrinic ring. Furthermore, the B and Q bands in the calculated spectrum are assigned to the four frontier molecular orbitals as proposed by Gouterman for free-based porphyrins.

Influence of Controlled Viscous Dissipation on Propagation of Strongly Nonlinear Waves in Steel-Based Phononic Crystals

NASA Astrophysics Data System (ADS)

Herbold, Eric

2005-07-01

Strongly nonlinear phononic crystals were assembled from chains of stainless steel spheres with diameter 4.78 mm. Propagation of solitary waves and splitting of initial pulse into train of solitary waves excited by the impact of piston was investigated in different viscous media in experiments and in numerical calculations. Oil of various grades was used to introduce controlled dissipation into the system. Preliminary results indicate that splitting of the initial pulse into the train of solitary waves was dramatically influenced by viscosity. This work was supported by NSF (Grant No. DCMS03013220).

Design of universal parallel-transmit refocusing kT -point pulses and application to 3D T2 -weighted imaging at 7T.

PubMed

Gras, Vincent; Mauconduit, Franck; Vignaud, Alexandre; Amadon, Alexis; Le Bihan, Denis; Stöcker, Tony; Boulant, Nicolas

2018-07-01

T 2 -weighted sequences are particularly sensitive to the radiofrequency (RF) field inhomogeneity problem at ultra-high-field because of the errors accumulated by the imperfections of the train of refocusing pulses. As parallel transmission (pTx) has proved particularly useful to counteract RF heterogeneities, universal pulses were recently demonstrated to save precious time and computational efforts by skipping B 1 calibration and online RF pulse tailoring. Here, we report a universal RF pulse design for non-selective refocusing pulses to mitigate the RF inhomogeneity problem at 7T in turbo spin-echo sequences with variable flip angles. Average Hamiltonian theory was used to synthetize a single non-selective refocusing pulse with pTx while optimizing its scaling properties in the presence of static field offsets. The design was performed under explicit power and specific absorption rate constraints on a database of 10 subjects using a 8Tx-32Rx commercial coil at 7T. To validate the proposed design, the RF pulses were tested in simulation and applied in vivo on 5 additional test subjects. The root-mean-square rotation angle error (RA-NRMSE) evaluation and experimental data demonstrated great improvement with the proposed universal pulses (RA-NRMSE ∼8%) compared to the standard circularly polarized mode of excitation (RA-NRMSE ∼26%). This work further completes the spectrum of 3D universal pulses to mitigate RF field inhomogeneity throughout all 3D MRI sequences without any pTx calibration. The approach returns a single pulse that can be scaled to match the desired flip angle train, thereby increasing the modularity of the proposed plug and play approach. Magn Reson Med 80:53-65, 2018. © 2017 International Society for Magnetic Resonance in Medicine. © 2017 International Society for Magnetic Resonance in Medicine.

Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules

NASA Astrophysics Data System (ADS)

Sturm, Felix; Ray, Dipanwita; Wright, Travis; Shivaram, Niranjan; Bocharova, Irina; Slaughter, Daniel; Ranitovic, Predrag; Belkacem, Ali; Weber, Thorsten

2016-05-01

Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O2+and the O+ ion yields with attosecond precision. Supported by DOE under Contract No. DE-AC02-05CH11231.

Optimization of passively mode-locked quasi-continuously diode-pumped Nd:GdVO4 laser in bounce geometry

NASA Astrophysics Data System (ADS)

Frank, Milan; Jelínek, Michal; Kubeček, Václav

2015-01-01

In this paper the operation of pulsed diode-pumped Nd:GdVO4 laser oscillator in bounce geometry passively modelocked using semiconductor saturable absorber mirror (SAM), generating microjoule level picosecond pulses at wavelength of 1063 nm, is reported. Optimization of the output coupling for generation either Q-switched mode locked pulse trains or cavity dumped single pulses with maximum energy was performed, which resulted in extraction of single pulses as short as 10 ps and energy of 20 uJ. In comparison with the previous results obtained with this Nd:GdVO4 oscillator and saturable absorber in transmission mode, the achieved pulse duration is five times shorter. Using different absorbers and parameters of single pulse extraction enables generation of the pulses with duration up to 100 ps with the energy in the range from 10 to 20 μJ.

Conductive graphene as passive saturable absorber with high instantaneous peak power and pulse energy in Q-switched regime

NASA Astrophysics Data System (ADS)

Zuikafly, Siti Nur Fatin; Khalifa, Ali; Ahmad, Fauzan; Shafie, Suhaidi; Harun, SulaimanWadi

2018-06-01

The Q-switched pulse regime is demonstrated by integrating conductive graphene as passive saturable absorber producing relatively high instantaneous peak power and pulse energy. The fabricated conductive graphene is investigated using Raman spectroscopy. The single wavelength Q-switching operates at 1558.28 nm at maximum input pump power of 151.47 mW. As the pump power is increased from threshold power of 51.6 mW to 151.47 mW, the pulse train repetition rate increases proportionally from 47.94 kHz to 67.8 kHz while the pulse width is reduced from 9.58 μs to 6.02 μs. The generated stable pulse produced maximum peak power and pulse energy of 32 mW and 206 nJ, respectively. The first beat node of the measured signal-to-noise ratio is about 62 dB indicating high pulse stability.

A pulse-burst laser system for a high-repetition-rate Thomson scattering diagnostic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Den Hartog, D. J.; Jiang, N.; Lempert, W. R.

2008-10-15

A ''pulse-burst'' laser system is being constructed for addition to the Thomson scattering diagnostic on the Madison Symmetric Torus (MST) reversed-field pinch. This laser is designed to produce a burst of up to 200 approximately 1 J Q-switched pulses at repetition frequencies 5-250 kHz. This laser system will operate at 1064 nm and is a master oscillator, power amplifier. The master oscillator is a compact diode-pumped Nd:YVO{sub 4} laser, intermediate amplifier stages are flashlamp-pumped Nd:YAG, and final stages will be flashlamp-pumped Nd:glass (silicate). Variable pulse width drive (0.3-20 ms) of the flashlamps is accomplished by insulated-gate bipolar transistor switching ofmore » large electrolytic capacitor banks. The burst train of laser pulses will enable the study of electron temperature (T{sub e}) and electron density (n{sub e}) dynamics in a single MST shot, and with ensembling, will enable correlation of T{sub e} and n{sub e} fluctuations with other fluctuating quantities.« less

Cardiac transient outward potassium current: a pulse chemistry model of frequency-dependent properties.

PubMed

Liu, L; Krinsky, V I; Grant, A O; Starmer, C F

1996-01-01

Recent voltage-clamp studies of isolated myocytes have demonstrated widespread occurrence of a transient outward current (I(to)) carried by potassium ions. In the canine ventricle, this current is well developed in epicardial cells but not in endocardial cells. The resultant spatial dispersion of refractoriness is potentially proarrhythmic and may be amplified by channel blockade. The inactivation and recovery time constants of this channel are in excess of several hundred milliseconds, and consequently channel availability is frequency dependent at physiological stimulation rates. When the time constants associated with transitions between different channel conformations are rapid relative to drug binding kinetics, the interactions between drugs and an ion channel can be approximated by a sequence of first-order reactions, in which binding occurs in pulses in response to pulse train stimulation (pulse chemistry). When channel conformation transition time constants do not meet this constraint, analytical characterizations of the drug-channel interaction must then be modified to reflect the channel time-dependent properties. Here we report that the rate and steady-state amount of frequency-dependent inactivation of I(to) are consistent with a generalization of the channel blockade model: channel availability is reduced in a pulsatile exponential pattern as the stimulation frequency is increased, and the rate of reduction is a linear function of the pulse train depolarizing and recovery intervals. I(to) was reduced in the presence of quinidine. After accounting for the use-dependent availability of I(to) channels, we found little evidence of an additional use-dependent component of block after exposure to quinidine, suggesting that quinidine reacts with both open and closed I(to) channels as though the binding site is continuously accessible. The model provides a useful tool for assessing drug-channel interactions when the reaction cannot be continuously monitored.

Higher-order power harmonics of pulsed electrical stimulation modulates corticospinal contribution of peripheral nerve stimulation.

PubMed

Chen, Chiun-Fan; Bikson, Marom; Chou, Li-Wei; Shan, Chunlei; Khadka, Niranjan; Chen, Wen-Shiang; Fregni, Felipe

2017-03-03

It is well established that electrical-stimulation frequency is crucial to determining the scale of induced neuromodulation, particularly when attempting to modulate corticospinal excitability. However, the modulatory effects of stimulation frequency are not only determined by its absolute value but also by other parameters such as power at harmonics. The stimulus pulse shape further influences parameters such as excitation threshold and fiber selectivity. The explicit role of the power in these harmonics in determining the outcome of stimulation has not previously been analyzed. In this study, we adopted an animal model of peripheral electrical stimulation that includes an amplitude-adapted pulse train which induces force enhancements with a corticospinal contribution. We report that the electrical-stimulation-induced force enhancements were correlated with the amplitude of stimulation power harmonics during the amplitude-adapted pulse train. In an exploratory analysis, different levels of correlation were observed between force enhancement and power harmonics of 20-80 Hz (r = 0.4247, p = 0.0243), 100-180 Hz (r = 0.5894, p = 0.0001), 200-280 Hz (r = 0.7002, p < 0.0001), 300-380 Hz (r = 0.7449, p < 0.0001), 400-480 Hz (r = 0.7906, p < 0.0001), 500-600 Hz (r = 0.7717, p < 0.0001), indicating a trend of increasing correlation, specifically at higher order frequency power harmonics. This is a pilot, but important first demonstration that power at high order harmonics in the frequency spectrum of electrical stimulation pulses may contribute to neuromodulation, thus warrant explicit attention in therapy design and analysis.

Radio frequency phototube

DOEpatents

Margaryan, Amur [Yerevan, AM; Gynashyan, Karlen [Yerevan, AM; Hashimoto, Osamu [Sendai, JP; Majewski, Stanislaw [Morgantown, WV; Tang, Linguang [Yorktown, VA; Marikyan, Gagik [Yerevan, AM; Marikyan, legal representative, Lia

2012-03-20

A method and apparatus of obtaining a record of repetitive optical or other phenomena having durations in the picosecond range, comprising a circular scan electron tube to receive light pulses and convert them to electron images consisting with fast nanosecond electronic signals, a continuous wave light or other particle pulses, e.g. electron picosecond pulses, and a synchronizing mechanism arranged to synchronize the deflection of the electron image (images) in the tube (tubes) with the repetition rate of the incident pulse train. There is also provided a method and apparatus for digitization of a repetitive and random optical waveform with a bandwidth higher than 10 GHz.

Pulse repetition rate multiplication by Talbot effect in a coaxial fiber

NASA Astrophysics Data System (ADS)

Dhingra, Nikhil; Saxena, Geetika Jain; Anand, Jyoti; Sharma, Enakshi K.

2018-03-01

We use a coaxial fiber, which is a cylindrical coupled waveguide structure consisting of two concentric cores, the inner rod and an outer ring core as a first order dispersive media to achieve temporal Talbot effect for pulse repetition rate multiplication (PRRM) in high bit rate optical fiber communication. It is observed that for an input Gaussian pulse train with pulse width, 2τ0=1ps at a repetition rate of 40 Gbps (repetition period, T=25ps), an output repetition rate of 640 Gbps can be achieved without significant distortion at a length of 40.92 m.

Sex differences in ventricular-vascular coupling following endurance training.

PubMed

Lane, A D; Yan, H; Ranadive, S M; Kappus, R M; Sun, P; Cook, M D; Harvey, I; Woods, J; Wilund, K; Fernhall, B

2014-12-01

Ventricular and vascular coupling is defined as the ratio of arterial elastance (Ea) to ventricular elastance (Elv) and describes the interaction between the heart and arterial system. There are sex differences in both arterial and ventricular function in response to both acute exercise and aerobic exercise training. To examine the effects of aerobic exercise training on elastances and the coupling ratio in young adult men and women. We hypothesized a reduction in the coupling ratio in both sexes due to a decrease in Ea that would be more pronounced in men and an increase in Elv that would be larger in women. Fifty-three healthy, young adults completed the study. Central pulse wave velocity and heart volumes were measured before and after an 8-week aerobic training intervention. Elastances were calculated as Ea = end-systolic pressure/stroke volume and Elv = end-systolic pressure/end-systolic volume and indexed to body surface area. After the intervention, women augmented indexed and un-indexed Elv from 2.09 ± 0.61 to 2.52 ± 0.80 mmHg/ml, p < 0.05, and reduced the coupling ratio from 0.72 ± 18 to 0.62 ± 15, p < 0.05, while men maintained their pre-training ratio (from 0.66 ± 0.20 to 0.74 ± 0.21, p > 0.05). Women also reduced end-systolic pressure (from 91 ± 10 to 87 ± 10 mmHg), and both groups reduced central pulse wave velocity (from 6.0 ± 1.0 to 5.6 ± 0.6 m/s, p < 0.05). We conclude that after 8 weeks of aerobic training, only women reduced their coupling ratio due to an increase in Elv. This suggests that aerobic exercise training elicits sex-dependent changes in the coupling ratio in young, healthy individuals.

Acute effects of interval versus continuous endurance training on pulse wave reflection in healthy young men.

PubMed

Hanssen, Henner; Nussbaumer, Monique; Moor, Christoph; Cordes, Mareike; Schindler, Christian; Schmidt-Trucksäss, Arno

2015-02-01

Our aim was to investigate the acute and 24-hour (h) effects of high-intensity interval training (HIIT) and moderate continuous training (MCT) on arterial pulse wave reflection, an established marker of arterial stiffness and cardiovascular risk. In a randomized cross-over design, 21 young healthy male participants performed a HIIT or a MCT on separate visits. Before and 5 (t5), 20 (t20), 35 (t35), and 50 (t50) minutes after the acute exercise bouts, the crude augmentation index (AIx) and the AIx at a set heart rate (AIx@75) were analysed by applanation tonometry. Starting 1 h post-exercise, both indices were captured over 24-h with an oscillometric monitoring device. AIx did not change significantly after MCT but declined progressively after HIIT, reaching significantly lower values compared to MCT at t35 (P = 0.045) and t50 (P = 0.008). AIx@75 increased after both acute exercise types but was higher after HIIT at t5 (P < 0.001), t20 (P < 0.001) and t35 (P = 0.009) compared to MCT. The 24-h follow-up revealed a significant decline in AIx@75 after HIIT (P = 0.007) but not after MCT (P = 0.813). Exercise intensity affects pulse wave reflection, with different time courses for AIx and AIx@75 post-exercise. Although initially higher after HIIT, AIx@75 declines in the 24-h recovery period indicating more favourable effects on pulse wave reflection compared to MCT. This may result in substantial positive chronic training effects on arterial stiffness in health and cardiovascular disease. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Responses of the circadian system of rats to conditioned and unconditioned stimuli.

PubMed

de Groot, M H; Rusak, B

2000-08-01

The circadian systems of rodents respond to light pulses presented during the subjective night with phase shifts and altered cellular activity in the suprachiasmatic nuclei (SCN), including expression of immediate-early genes (IEGs) such as c-fos. A recent study showed that a nonphotic stimulus (an air disturbance generated by a fan) that does not normally induce the expression of c-fos-like immunoreactivity in the SCN of rats can be made to do so after being paired repeatedly with a light pulse in a Pavlovian conditioning paradigm. Furthermore, after conditioning (but not after noncontingent exposure to these stimuli), the fan also induced phase shifts in activity and body temperature rhythms comparable to those produced by light. The authors performed three experiments designed to replicate and extend these findings in rats. In experiment 1, rats were tested for conditioning effects of repeated pairings of a light pulse with a neutral air disturbance under a full photoperiod. In experiment 2, a modified conditioning paradigm was used in which a skeleton photoperiod served as both the entraining zeitgeber and the unconditioned stimulus. Animals in the paired and unpaired training conditions were exposed to both the light pulse and the air disturbance, but the air disturbance signaled the onset of light in the paired condition only. Phase shifts of wheel-running activity rhythms and gene expression in the SCN, intergeniculate leaflet, and paraventricular nucleus of the thalamus were assessed in animals following either of the training conditions or the control procedures. Experiment 3 assessed whether the air disturbance could entrain the circadian activity rhythms of rats with or without previous pairing with light in a classical conditioning paradigm. No evidence for classical conditioning, nor for unconditioned effects of the air disturbance on the circadian system, was found in these studies.

Effect of laser pulse repetition frequency on the optical breakdown threshold of quartz glass

NASA Astrophysics Data System (ADS)

Kononenko, T. V.; Schöneseiffen, S.; Konov, V. I.; Dausinger, F.

2013-08-01

The thresholds of optical breakdown in the volume of quartz glass were measured in relation to the number of pulses under irradiation by ultrashort laser pulses with different pulse repetition frequencies (1 - 400 kHz). Increasing this frequency from 10 to 400 kHz was found to substantially lower the breakdown threshold for 500-fs long pulses (at a wavelength of 1030 nm) and to lower to a smaller degree for 5-ps long pulses (515 nm). A strong frequency dependence of the breakdown threshold is observed under the same conditions as a manifold decrease of the breakdown threshold with increase in the number of pulses in a pulse train. The dependence of the optical breakdown on the number of pulses is attributable to the accumulation of point defects under multiple subthreshold irradiation, which affects the mechanism of collisional ionisation. In this case, the frequency dependence of the breakdown threshold of quartz glass is determined by the engagement of shortlived defects in the ionisation mechanism.

Generation of switchable domain wall and Cubic-Quintic nonlinear Schrödinger equation dark pulse

NASA Astrophysics Data System (ADS)

Tiu, Z. C.; Suthaskumar, M.; Zarei, A.; Tan, S. J.; Ahmad, H.; Harun, S. W.

2015-10-01

A switchable domain-wall (DW) and Cubic-Quintic nonlinear Schrödinger equation (CQNLSE) dark soliton pulse generation are demonstrated in Erbium-doped fiber laser (EDFL) for the first time. The DW pulse train operates at 1575 nm with a fundamental repetition rate of 1.52 MHz and pulse width of 203 ns as the pump power is increased above the threshold pump power of 80 mW. The highest pulse energy of 2.24 nJ is obtained at the maximum pump power of 140 mW. CQNLSE pulse can also be realized from the same cavity by adjusting the polarization state but at a higher threshold pump power of 104 mW. The repetition rate and pulse width of the CQNLSE dark pulses are obtained at 1.52 MHz and 219 ns, respectively. The highest energy of 0.58 nJ is obtained for the CQNLSE pulse at pump power of 140 mW.

Efficient photoassociation of ultracold cesium atoms with picosecond pulse laser

NASA Astrophysics Data System (ADS)

Hai, Yang; Hu, Xue-Jin; Li, Jing-Lun; Cong, Shu-Lin

2017-08-01

We investigate theoretically the formation of ultracold Cs2 molecules via photoassociation (PA) with three kinds of pulses (the Gaussian pulse, the asymmetric shaped laser pulse SL1 with a large rising time and a small falling time and the asymmetric shaped laser pulse SL2 with a small rising time and a large falling time). For the three kinds of pulses, the final population on vibrational levels from v‧ = 120 to 175 of the excited state displays a regular oscillation change with pulse width and interaction strength, and a high PA efficiency can be achieved with optimised parameters. The PA efficiency in the excited state steered by the SL1-pulse (SL2-pulse) train with optimised parameters which is composed of four SL1 (SL2) pulses is 1.74 times as much as that by the single SL1 (SL2) pulse due to the population accumulation effect. Moreover, a dump laser is employed to transfer the excited molecules from the excited state to the vibrational level v″ = 12 of the ground state to obtain stable molecules.

Slow Temporal Summation of Pain for Assessment of Central Pain Sensitivity and Clinical Pain of Fibromyalgia Patients

PubMed Central

Staud, Roland; Weyl, Elizabeth E.; Riley, Joseph L.; Fillingim, Roger B.

2014-01-01

Background In healthy individuals slow temporal summation of pain or wind-up (WU) can be evoked by repetitive heat-pulses at frequencies of ≥.33 Hz. Previous WU studies have used various stimulus frequencies and intensities to characterize central sensitization of human subjects including fibromyalgia (FM) patients. However, many trials demonstrated considerable WU-variability including zero WU or even wind-down (WD) at stimulus intensities sufficient for activating C-nociceptors. Additionally, few WU-protocols have controlled for contributions of individual pain sensitivity to WU-magnitude, which is critical for WU-comparisons. We hypothesized that integration of 3 different WU-trains into a single WU-response function (WU-RF) would not only control for individuals’ pain sensitivity but also better characterize their central pain responding including WU and WD. Methods 33 normal controls (NC) and 38 FM patients participated in a study of heat-WU. We systematically varied stimulus intensities of.4 Hz heat-pulse trains applied to the hands. Pain summation was calculated as difference scores of 1st and 5th heat-pulse ratings. WU-difference (WU-Δ) scores related to 3 heat-pulse trains (44°C, 46°C, 48°C) were integrated into WU-response functions whose slopes were used to assess group differences in central pain sensitivity. WU-aftersensations (WU-AS) at 15 s and 30 s were used to predict clinical FM pain intensity. Results WU-Δ scores linearly accelerated with increasing stimulus intensity (p<.001) in both groups of subjects (FM>NC) from WD to WU. Slope of WU-RF, which is representative of central pain sensitivity, was significantly steeper in FM patients than NC (p<.003). WU-AS predicted clinical FM pain intensity (Pearson’s r = .4; p<.04). Conclusions Compared to single WU series, WU-RFs integrate individuals’ pain sensitivity as well as WU and WD. Slope of WU-RFs was significantly different between FM patients and NC. Therefore WU-RF may be useful for assessing central sensitization of chronic pain patients in research and clinical practice. PMID:24558475

The effect of a lignosulphate type additive on the lead—acid battery positive plate reactions

NASA Astrophysics Data System (ADS)

Ovuru, S. E.; Harrison, J. A.

The electrochemical formation of lead dioxide has been investigated at a lead electrode in a 5 M sulphuric acid solution, and in the presence of phosphoric acid and lignosulphate-type additive. The formation of lead dioxide from lead sulphate, and the reverse reaction, have been investigated by the linear potential sweep method, by an impedance method in which the impedance was measured at the end of each pulse during a potential pulse train, and by a charging curve method in which the current and charge was measured during a similar potential pulse train. The charge measurements prove that the main effect of the additive is to decrease the accompanying oxygen evolution reaction. The impedance measurements, however, show that the additive has a small but significant effect on the structure of the solid lead sulphate and lead dioxide layers.

Effects of U.S. Navy Diver Training on Physiological Parameters, Time of Useful Consciousness and Cognitive Performance During Periods of Normobaric Hypoxia

DTIC Science & Technology

2014-04-01

from the pulse oximeter were integrated, digitized, and displayed graphically in real time in LabView (National Instruments) and logged at 20 Hz...Peripheral oxygenation monitoring: Fg-SpO2 levels were measured using a pulse oximeter placed on the left index finger (ROBD-2; Series 6202, Environics...Tolland, CT). Heart rate monitoring: HR was measured using a pulse oximeter placed on the left index finger (ROBD-2; Series 6202, Environics

Effects of U.S. Navy Diver Training on Physiological Parameters, Time of Useful Consciousness, and Cognitive Performance During Periods of Normobaric Hypoxia

DTIC Science & Technology

2014-04-01

from the pulse oximeter were integrated, digitized, and displayed graphically in real time in LabView (National Instruments) and logged at 20 Hz...Peripheral oxygenation monitoring: Fg-SpO2 levels were measured using a pulse oximeter placed on the left index finger (ROBD-2; Series 6202, Environics...Tolland, CT). Heart rate monitoring: HR was measured using a pulse oximeter placed on the left index finger (ROBD-2; Series 6202, Environics

A unique modulation system for two channel data transmission

NASA Technical Reports Server (NTRS)

Melrose, B. T.

1972-01-01

A simple low cost system is reported for the telemetry of information from meteorological rocket payloads including parachute borne systems. It uses S- or L-band microwave links with low cost oscillator type transmitters. An extension of this system to transmit two channels of data simultaneously by standard time and frequency multiplexing techniques as a sampled pulse is described. One channel is represented by the pulse repetition rate while the other channel is represented by the instantaneous duty cycle of the pulse train.

ARPA Semiannual Technical Report, Materials Science

DTIC Science & Technology

1973-12-15

determine the oscillator output properties. A newly designed cylindrical-ring-electrode Pockel’s cell is used for single picosecond pulse...satellite pulse trains and pulse noise. A contacted dye cell has been constructed and tested for this new system. Considerable experience in its ur-e...by the definition - - - -- ■’ -’ ’" - - ■ - - ■; - . v -• . . . -. 1.,-. •. • .’■-."■ ’,■■ . • ’*■ ," ’".** "."’" ", ■," ■T^r,T^" nT1

Effect of whole body resistance training on arterial compliance in young men.

PubMed

Rakobowchuk, M; McGowan, C L; de Groot, P C; Bruinsma, D; Hartman, J W; Phillips, S M; MacDonald, M J

2005-07-01

The effect of resistance training on arterial stiffening is controversial. We tested the hypothesis that resistance training would not alter central arterial compliance. Young healthy men (age, 23 +/- 3.9 (mean +/- s.e.m.) years; n = 28,) were whole-body resistance trained five times a week for 12 weeks, using a rotating 3-day split-body routine. Resting brachial blood pressure (BP), carotid pulse pressure, carotid cross-sectional compliance (CSC), carotid initima-media thickness (IMT) and left ventricular dimensions were evaluated before beginning exercise (PRE), after 6 weeks of exercise (MID) and at the end of 12 weeks of exercise (POST). CSC was measured using the pressure-sonography method. Results indicate reductions in brachial (61.1 +/- 1.4 versus 57.6 +/- 1.2 mmHg; P < 0.01) and carotid pulse pressure (52.2 +/- 1.9 versus 46.8 +/- 2.0 mmHg; P < 0.01) PRE to POST. In contrast, carotid CSC, beta-stiffness index, IMT and cardiac dimensions were unchanged. In young men, central arterial compliance is unaltered with 12 weeks of resistance training and the mechanisms responsible for cardiac hypertrophy and reduced arterial compliance are either not inherent to all resistance-training programmes or may require a prolonged stimulus.

Analysis of originating ultra-short optical dissipative solitary pulses in the actively mode-locked semiconductor heterolasers with an external fiber cavity

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Campos Acosta, Joaquin; Pons Aglio, Alicia; Moreno Zarate, Pedro; Mansurova, Svetlana

2010-06-01

We present an advanced approach to describing low-power trains of bright picosecond optical dissipative solitary pulses with an internal frequency modulation in practically important case of exploiting semiconductor heterolaser operating in near-infrared range in the active mode-locking regime. In the chosen schematic arrangement, process of the active mode-locking is caused by a hybrid nonlinear cavity consisting of this heterolaser and an external rather long single-mode optical fiber exhibiting square-law dispersion, cubic Kerr nonlinearity, and small linear optical losses. Our analysis of shaping dissipative solitary pulses includes three principal contributions associated with the modulated gain, total optical losses, as well as with linear and nonlinear phase shifts. In fact, various trains of the non-interacting to one another optical dissipative solitons appear within simultaneous balance between the second-order dispersion and cubic-law Kerr nonlinearity as well as between active medium gain and linear optical losses in a hybrid cavity. Our specific approach makes possible taking the modulating signals providing non-conventional composite regimes of a multi-pulse active mode-locking. Within our model, a contribution of the appearing nonlinear Ginzburg-Landau operator to the parameters of dissipative solitary pulses is described via exploiting an approximate variational procedure involving the technique of trial functions.

Autogenic training to reduce anxiety in nursing students: randomized controlled trial.

PubMed

Kanji, Nasim; White, Adrian; Ernst, Edzard

2006-03-01

This paper reports a study to determine the effectiveness of autogenic training in reducing anxiety in nursing students. Nursing is stressful, and nursing students also have the additional pressures and uncertainties shared with all academic students. Autogenic training is a relaxation technique consisting of six mental exercises and is aimed at relieving tension, anger and stress. Meta-analysis has found large effect sizes for autogenic trainings intervention comparisons, medium effect sizes against control groups, and no effects when compared with other psychological therapies. A controlled trial with 50 nursing students found that the number of certified days off sick was reduced by autogenic training compared with no treatment, and a second trial with only 18 students reported greater improvement in Trait Anxiety, but not State Anxiety, compared with untreated controls. A randomized controlled trial with three parallel arms was completed in 1998 with 93 nursing students aged 19-49 years. The setting was a university college in the United Kingdom. The treatment group received eight weekly sessions of autogenic training, the attention control group received eight weekly sessions of laughter therapy, and the time control group received no intervention. The outcome measures were the State-Trait Anxiety Inventory, the Maslach Burnout Inventory, blood pressure and pulse rate completed at baseline, 2 months (end of treatment), and 5, 8, and 11 months from randomization. There was a statistically significantly greater reduction of State (P<0.001) and Trait (P<0.001) Anxiety in the autogenic training group than in both other groups immediately after treatment. There were no differences between the groups for the Maslach Burnout Inventory. The autogenic training group also showed statistically significantly greater reduction immediately after treatment in systolic (P<0.01) and diastolic (P<0.05) blood pressure, and pulse rate (P<0.002), than the other two groups. CONCLUSION. Autogenic training has at least a short-term effect in alleviating stress in nursing students.

Biphasic pulses enhance bleomycin efficacy in a spontaneous canine genital tumor model of chemoresistance: Sticker sarcoma

PubMed Central

Spugnini , Enrico P; Dotsinsky , Ivan; Mudrov , Nikolay; Citro , Gennaro; D'Avino , Alfredo; Baldi , Alfonso

2008-01-01

Sticker's sarcoma (also known as transmissible venereal tumor) is a horizontally transmitted neoplasm of the dog, that is passed with coitus. It is a locally aggressive tumor with a low tendency to metastatic spread. The most common locations are the genitals, the nose, the perianal area. Standard treatment consists with chemotherapy with vincristine, however other therapies such as, cryotherapy, immunotherapy or, in selected cases, radiation therapy, have been reported. In this article we describe the outcome of a small cohort of canine patients, with chemotherapy resistant transmissible venereal tumor (TVT), treated with bleomycin selectively driven by trains of biphasic pulses (electrochemotherapy). Three canine patients, with refractory TVT, entered the study and received two sessions of ECT under sedation. The pets had local injection of bleomycin at the concentration of 1.5 mg/ml and five minutes after the chemotherapy, trains of 8 biphasic electric pulses lasting 50 + 50 μs each, with 1 ms interpulse intervals, were delivered by means of modified caliper or, for difficult districts, through paired needle electrode. All the patients responded to the treatment and are still in remission at different times. Electrochemotherapy appears as a safe and efficacious modality for the treatment of TVT and warrants further investigations. PMID:18980687

Inverted-U Function Relating Cortical Plasticity and Task Difficulty

PubMed Central

Engineer, Navzer D.; Engineer, Crystal T.; Reed, Amanda C.; Pandya, Pritesh K.; Jakkamsetti, Vikram; Moucha, Raluca; Kilgard, Michael P.

2012-01-01

Many psychological and physiological studies with simple stimuli have suggested that perceptual learning specifically enhances the response of primary sensory cortex to task-relevant stimuli. The aim of this study was to determine whether auditory discrimination training on complex tasks enhances primary auditory cortex responses to a target sequence relative to non-target and novel sequences. We collected responses from more than 2,000 sites in 31 rats trained on one of six discrimination tasks that differed primarily in the similarity of the target and distractor sequences. Unlike training with simple stimuli, long-term training with complex stimuli did not generate target specific enhancement in any of the groups. Instead, cortical receptive field size decreased, latency decreased, and paired pulse depression decreased in rats trained on the tasks of intermediate difficulty while tasks that were too easy or too difficult either did not alter or degraded cortical responses. These results suggest an inverted-U function relating neural plasticity and task difficulty. PMID:22249158

Method of estimating pulse response using an impedance spectrum

DOEpatents

Morrison, John L; Morrison, William H; Christophersen, Jon P; Motloch, Chester G

2014-10-21

Electrochemical Impedance Spectrum data are used to predict pulse performance of an energy storage device. The impedance spectrum may be obtained in-situ. A simulation waveform includes a pulse wave with a period greater than or equal to the lowest frequency used in the impedance measurement. Fourier series coefficients of the pulse train can be obtained. The number of harmonic constituents in the Fourier series are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency used in the impedance measurement. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at corresponding frequencies to obtain Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed and reassembled to obtain the overall time domain estimate of the voltage using the Fourier series analysis.

Alleviation of pressure pulse effects for trains entering tunnels. Volume 1: Summary

NASA Technical Reports Server (NTRS)

Dayman, B., Jr.; Hammitt, A. G.; Holway, H. P.; Tucker, C. E., Jr.; Vardy, A. E.

1979-01-01

The degree to which it is possible to attenuate the effects of pressure pulses on the passengers in trains entering tunnels by modifying the normally abrupt portal of a constant-diameter single track tunnel was investigated. Although the suggested modifications to the tunnel entrance portal may not appreciably decrease the magnitude of the pressure rise, they are very effective in reducing the discomfort to the human ear by substantially decreasing the rate of pressure rise to that which the normal ear can accommodate. Qualitative comparison was made of this portal modification approach with other approaches: decreasing the train speed or sealing the cars. The optimum approach, which is dependent upon the conditions and requirements of each particular rail system, is likely to be the portal modification one for a rapid rail mass transit system.

Sub-femtosecond timing jitter, all-fiber, CNT-mode-locked Er-laser at telecom wavelength.

PubMed

Kim, Chur; Bae, Sangho; Kieu, Khanh; Kim, Jungwon

2013-11-04

We demonstrate a 490-attosecond timing jitter (integration bandwidth: 10 kHz - 39.4 MHz) optical pulse train from a 78.7-MHz repetition rate, all-fiber soliton Er laser mode-locked by a fiber tapered carbon nanotube saturable absorber (ft-CNT-SA). To achieve this jitter performance, we searched for a net cavity dispersion condition where the Gordon-Haus jitter is minimized while maintaining stable soliton mode-locking. Our result shows that optical pulse trains with well below a femtosecond timing jitter can be generated from a self-starting and robust all-fiber laser operating at telecom wavelength.

Stable passive optical clock generation in SOA-based fiber lasers.

PubMed

Wang, Jing-Yun; Lin, Kuei-Huei; Chen, Hou-Ren

2015-02-15

Stable optical pulse trains are obtained from 1.3-μm and 1.5-μm semiconductor optical amplifier (SOA)-based fiber lasers using passive optical technology. The waveforms depend on SOA currents, and the repetition rates can be tuned by varying the relative length of sub-cavities. The output pulse trains of these SOA-based fiber lasers are stable against intracavity polarization adjustment and environmental perturbation. The optical clock generation is explained in terms of mode competition, self-synchronization, and SOA saturation. Without resorting to any active modulation circuits or devices, the technology used here is simple and may find various applications in the future.

On the Morphological Adaptations of the Thorax of Sphagniana sphagnorum (Ensifera, Tettigoniidae) that Enable Complex Stridulation via the Forewings

NASA Astrophysics Data System (ADS)

Gutierrez, Sara-Jane

Males of the flightless tettigoniid Sphagniana sphagnorum generate a complex two-spectrum signal via stridulation, using acoustically adapted forewings (tegmina). Complex-wave rapidly decaying pulses in trains, made upon the distal half of the file, have a broad-band (17-25 kHz) spectrum; short, spaced, ultrasonic and strongly sinusoidal 35 kHz pulses are emitted as trains over the file's proximal half. I studied how S. sphagnorum tegminal morphology enables the production of these two different spectra with the same forewings. The storage of elastic energy in the scraper is hypothesized to play a key role in driving the scraper over the file at a necessary tooth-contact rate. Scraper morphology indicates structural adaptations enabling storage of elastic energy. Wax loading tested the role of scraper-pit flexibility in scraper movement. Sound levels in resonant spectra were more substantially affected than those associated with broadband generation. Morphology and alignment of pteralia during tegmino-tegminal stridulation is also investigated.

Terahertz demultiplexing by a single-shot time-to-space conversion using a film of squarylium dye J aggregates

NASA Astrophysics Data System (ADS)

Furuki, Makoto; Tian, Minquan; Sato, Yasuhiro; Pu, Lyong Sun; Tatsuura, Satoshi; Wada, Osamu

2000-07-01

We applied time-to-space conversion using femtosecond nonlinear-optical response of squarylium-dye (SQ) J-aggregates film. A pump pulse and a train of four probe pulses were illuminated on the same area (10 mm φ) of the film in direction of oblique and normal to the film plane, respectively. Due to the oblique illumination, the pump pulse met probe pulses (interval time: 1 ps) at separate places. The film picked out part of each probe pulse by its transmittance change, which was observed for a transmitted image of spatially separated four lines. Response time of the SQ J aggregates is enough for the single-shot 1 THz demultiplexing.

Motor Training Promotes Both Synaptic and Intrinsic Plasticity of Layer II/III Pyramidal Neurons in the Primary Motor Cortex

PubMed Central

Kida, Hiroyuki; Tsuda, Yasumasa; Ito, Nana; Yamamoto, Yui; Owada, Yuji; Kamiya, Yoshinori; Mitsushima, Dai

2016-01-01

Motor skill training induces structural plasticity at dendritic spines in the primary motor cortex (M1). To further analyze both synaptic and intrinsic plasticity in the layer II/III area of M1, we subjected rats to a rotor rod test and then prepared acute brain slices. Motor skill consistently improved within 2 days of training. Voltage clamp analysis showed significantly higher α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/N-methyl-d-aspartate (AMPA/NMDA) ratios and miniature EPSC amplitudes in 1-day trained rats compared with untrained rats, suggesting increased postsynaptic AMPA receptors in the early phase of motor learning. Compared with untrained controls, 2-days trained rats showed significantly higher miniature EPSC amplitude and frequency. Paired-pulse analysis further demonstrated lower rates in 2-days trained rats, suggesting increased presynaptic glutamate release during the late phase of learning. One-day trained rats showed decreased miniature IPSC frequency and increased paired-pulse analysis of evoked IPSC, suggesting a transient decrease in presynaptic γ-aminobutyric acid (GABA) release. Moreover, current clamp analysis revealed lower resting membrane potential, higher spike threshold, and deeper afterhyperpolarization in 1-day trained rats—while 2-days trained rats showed higher membrane potential, suggesting dynamic changes in intrinsic properties. Our present results indicate dynamic changes in glutamatergic, GABAergic, and intrinsic plasticity in M1 layer II/III neurons after the motor training. PMID:27193420

Motor Training Promotes Both Synaptic and Intrinsic Plasticity of Layer II/III Pyramidal Neurons in the Primary Motor Cortex.

PubMed

Kida, Hiroyuki; Tsuda, Yasumasa; Ito, Nana; Yamamoto, Yui; Owada, Yuji; Kamiya, Yoshinori; Mitsushima, Dai

2016-08-01

Motor skill training induces structural plasticity at dendritic spines in the primary motor cortex (M1). To further analyze both synaptic and intrinsic plasticity in the layer II/III area of M1, we subjected rats to a rotor rod test and then prepared acute brain slices. Motor skill consistently improved within 2 days of training. Voltage clamp analysis showed significantly higher α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/N-methyl-d-aspartate (AMPA/NMDA) ratios and miniature EPSC amplitudes in 1-day trained rats compared with untrained rats, suggesting increased postsynaptic AMPA receptors in the early phase of motor learning. Compared with untrained controls, 2-days trained rats showed significantly higher miniature EPSC amplitude and frequency. Paired-pulse analysis further demonstrated lower rates in 2-days trained rats, suggesting increased presynaptic glutamate release during the late phase of learning. One-day trained rats showed decreased miniature IPSC frequency and increased paired-pulse analysis of evoked IPSC, suggesting a transient decrease in presynaptic γ-aminobutyric acid (GABA) release. Moreover, current clamp analysis revealed lower resting membrane potential, higher spike threshold, and deeper afterhyperpolarization in 1-day trained rats-while 2-days trained rats showed higher membrane potential, suggesting dynamic changes in intrinsic properties. Our present results indicate dynamic changes in glutamatergic, GABAergic, and intrinsic plasticity in M1 layer II/III neurons after the motor training. © The Author 2016. Published by Oxford University Press.

Repetitive transcranial magnetic stimulator with controllable pulse parameters

NASA Astrophysics Data System (ADS)

Peterchev, Angel V.; Murphy, David L.; Lisanby, Sarah H.

2011-06-01

The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10-310 µs and positive/negative phase amplitude ratio of 1-56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

Repetitive transcranial magnetic stimulator with controllable pulse parameters.

PubMed

Peterchev, Angel V; Murphy, David L; Lisanby, Sarah H

2011-06-01

The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10-310 µs and positive/negative phase amplitude ratio of 1-56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation up to 82% and 57% and decreases coil heating up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications and could lead to clinical applications with potentially enhanced potency.

Asynchronous sampling of speech with some vocoder experimental results

NASA Technical Reports Server (NTRS)

Babcock, M. L.

1972-01-01

The method of asynchronously sampling speech is based upon the derivatives of the acoustical speech signal. The following results are apparent from experiments to date: (1) It is possible to represent speech by a string of pulses of uniform amplitude, where the only information contained in the string is the spacing of the pulses in time; (2) the string of pulses may be produced in a simple analog manner; (3) the first derivative of the original speech waveform is the most important for the encoding process; (4) the resulting pulse train can be utilized to control an acoustical signal production system to regenerate the intelligence of the original speech.

Ultra-fast quantum randomness generation by accelerated phase diffusion in a pulsed laser diode.

PubMed

Abellán, C; Amaya, W; Jofre, M; Curty, M; Acín, A; Capmany, J; Pruneri, V; Mitchell, M W

2014-01-27

We demonstrate a high bit-rate quantum random number generator by interferometric detection of phase diffusion in a gain-switched DFB laser diode. Gain switching at few-GHz frequencies produces a train of bright pulses with nearly equal amplitudes and random phases. An unbalanced Mach-Zehnder interferometer is used to interfere subsequent pulses and thereby generate strong random-amplitude pulses, which are detected and digitized to produce a high-rate random bit string. Using established models of semiconductor laser field dynamics, we predict a regime of high visibility interference and nearly complete vacuum-fluctuation-induced phase diffusion between pulses. These are confirmed by measurement of pulse power statistics at the output of the interferometer. Using a 5.825 GHz excitation rate and 14-bit digitization, we observe 43 Gbps quantum randomness generation.

Ellipticity dependence of high harmonics generated using 400 nm driving lasers

NASA Astrophysics Data System (ADS)

Cheng, Yan; Khan, Sabih; Zhao, Kun; Zhao, Baozhen; Chini, Michael; Chang, Zenghu

2011-05-01

High order harmonics generated from 400 nm driving pulses hold promise of scaling photon flux of single attosecond pulses by one to two orders of magnitude. We report ellipticity dependence and phase matching of high order harmonics generated from such pulses in Neon gas target and compared them with similar measurements using 800 nm driving pulses. Based on measured ellipticity dependence, we predict that double optical gating (DOG) and generalized double optical gating (GDOG) can be employed to extract intense single attosecond pulses from pulse train, while polarization gating (PG) may not work for this purpose. This material is supported by the U.S. Army Research Office under grant number W911NF-07-1-0475, and by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Generation of “gigantic” ultra-short microwave pulses based on passive mode-locking effect in electron oscillators with saturable absorber in the feedback loop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginzburg, N. S., E-mail: ginzburg@appl.sci-nnov.ru; Denisov, G. G.; Vilkov, M. N.

2016-05-15

A periodic train of powerful ultrashort microwave pulses can be generated in electron oscillators with a non-linear saturable absorber installed in the feedback loop. This method of pulse formation resembles the passive mode-locking widely used in laser physics. Nevertheless, there is a specific feature in the mechanism of pulse amplification when consecutive energy extraction from different fractions of a stationary electron beam takes place due to pulse slippage over the beam caused by the difference between the wave group velocity and the electron axial velocity. As a result, the peak power of generated “gigantic” pulses can exceed not only themore » level of steady-state generation but also, in the optimal case, the power of the driving electron beam.« less

Q-switched erbium doped fiber laser based on single and multiple walled carbon nanotubes embedded in polyethylene oxide film as saturable absorber

NASA Astrophysics Data System (ADS)

Ahmed, M. H. M.; Ali, N. M.; Salleh, Z. S.; Rahman, A. A.; Harun, S. W.; Manaf, M.; Arof, H.

2015-01-01

A passive, stable and low cost Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using both single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs), which are embedded in polyethylene oxide (PEO) film as a saturable absorber (SA). The film is sandwiched between two FC/PC fiber connectors and integrated into the laser cavity for Q-switching pulse generation operating at wavelength of 1533.6 nm. With SWCNTs, the laser produces a stable pulse train with repetition rate and pulse width ranging from 9.52 to 33.33 kHz and 16.8 to 8.0 μs while varying the 980 nm pump power from 48.5 mW to 100.4 mW. On the other hand, with MWCNTs, the repetition rate and pulse width can be tuned in a wider range of 6.12-33.62 kHz and 9.5- 4.2 μs, respectively as the pump power increases from 37.9 to 120.6 mW. The MWCNTs produce the pulse train at a lower threshold and attain a higher repetition rate compared to the SWCNTs. This is due to thicker carbon nanotubes layer of the MWCNTs which provides more absorption and consequently higher damage threshold. The Q-switched EDFL produces the highest pulse energy of 531 nJ at pump power of 37.9 mW with the use of MWCNTs-PEO SA.

Saturation of subjective reward magnitude as a function of current and pulse frequency.

PubMed

Simmons, J M; Gallistel, C R

1994-02-01

In rats with electrodes in the medial forebrain bundle, the upper portion of the function relating the experienced magnitude of the reward to pulse frequency was determined at currents ranging from 100 to 1,000 microA. The pulse frequency required to produce an asymptotic level of reward was inversely proportional to current except at the lowest currents and highest pulse frequencies. At a given current, the subjective reward magnitude functions decelerated to an asymptote over an interval in which the pulse frequency doubled or tripled. The asymptotic level of reward was approximately constant for currents between 200 and 1,000 microA but declined substantially at currents at or below 100 microA and pulse frequencies at or above 250 to 400 pulses per second. The results are consistent with the hypothesis that the magnitude of the experienced reward depends only on the number of action potentials generated by the train of pulses in the bundle of reward-relevant axons.

An evaluation of the Exer-Genie exerciser and the Collins pedal mode ergometer for developing physical fitness

NASA Technical Reports Server (NTRS)

Olree, H. D.

1973-01-01

Experiments that were conducted over a 52-month period showed that isometric and isotonic training on the Exer-Genie gave negligible increases in cardiorespiratory fitness whereas training on the ergometer at a programmed pulse rate increased fitness moderately.

High pulse repetition frequency ultrasound system for ex vivo measurement of mechanical properties of crystalline lenses with laser-induced microbubble interrogated by acoustic radiation force

PubMed Central

Yoon, Sangpil; Aglyamov, Salavat; Karpiouk, Andrei; Emelianov, Stanislav

2012-01-01

A high pulse repetition frequency ultrasound system for ex vivo measurement of mechanical properties of animal crystalline lens was developed and validated. We measured the bulk displacement of laser-induced microbubbles created at different positions within the lens using nanosecond laser pulses. An impulsive acoustic radiation force was applied to the microbubble, and spatio-temporal measurements of the microbubble displacement were assessed using a custom-made high pulse repetition frequency ultrasound system consisting of two 25 MHz focused ultrasound transducers. One of these transducers was used to emit a train of ultrasound pulses and another transducer was used to receive the ultrasound echoes reflected from the microbubble. The developed system was operating at 1 MHz pulse repetition frequency. Based on measured motion of the microbubble, the Young’s moduli of surrounding tissue were reconstructed and the values were compared with those measured using indentation test. Measured values of Young’s moduli of 4 bovine lenses ranged from 2.6±0.1 to 26±1.4 kPa and there was good agreement between the two methods. Therefore, our studies, utilizing the high pulse repetition frequency ultrasound system, suggest that the developed approach can be used to assess the mechanical properties of ex vivo crystalline lenses. Furthermore, the potential of the presented approach for in vivo measurements is discussed. PMID:22797709

Application of a deconvolution method for identifying burst amplitudes and arrival times in Alcator C-Mod far SOL plasma fluctuations

NASA Astrophysics Data System (ADS)

Theodorsen, Audun; Garcia, Odd Erik; Kube, Ralph; Labombard, Brian; Terry, Jim

2017-10-01

In the far scrape-off layer (SOL), radial motion of filamentary structures leads to excess transport of particles and heat. Amplitudes and arrival times of these filaments have previously been studied by conditional averaging in single-point measurements from Langmuir Probes and Gas Puff Imaging (GPI). Conditional averaging can be problematic: the cutoff for large amplitudes is mostly chosen by convention; the conditional windows used may influence the arrival time distribution; and the amplitudes cannot be separated from a background. Previous work has shown that SOL fluctuations are well described by a stochastic model consisting of a super-position of pulses with fixed shape and randomly distributed amplitudes and arrival times. The model can be formulated as a pulse shape convolved with a train of delta pulses. By choosing a pulse shape consistent with the power spectrum of the fluctuation time series, Richardson-Lucy deconvolution can be used to recover the underlying amplitudes and arrival times of the delta pulses. We apply this technique to both L and H-mode GPI data from the Alcator C-Mod tokamak. The pulse arrival times are shown to be uncorrelated and uniformly distributed, consistent with a Poisson process, and the amplitude distribution has an exponential tail.

Nature of short, high-amplitude compressive stress pulses in a periodic dissipative laminate.

PubMed

Franco Navarro, Pedro; Benson, David J; Nesterenko, Vitali F

2015-12-01

We study the evolution of high-amplitude stress pulses in periodic dissipative laminates taking into account the nonlinear constitutive equations of the components and their dissipative behavior. Aluminum-tungsten laminate was selected due to the large difference in acoustic impedances of components, the significant nonlinearity of the aluminum constitutive equation at the investigated range of stresses, and its possible practical applications. Laminates with different cell size, which controls the internal time scale, impacted by plates with different thicknesses that determine the incoming pulse duration, were investigated. It has been observed that the ratio of the duration of the incoming pulse to the internal characteristic time determines the nature of the high-amplitude dissipative propagating waves-a triangular oscillatory shock-like profile, a train of localized pulses, or a single localized pulse. These localized quasistationary waves resemble solitary waves even in the presence of dissipation: The similar pulses emerged from different initial conditions, indicating that they are inherent properties of the corresponding laminates; their characteristic length scale is determined by the scale of mesostructure, nonlinear properties of materials, and the stress amplitude; and a linear relationship exists between their speed and amplitude. They mostly recover their shapes after collision with phase shift. A theoretical description approximating the shape, length scale, and speed of these high-amplitude dissipative pulses was proposed based on the Korteweg-de Vries equation with a dispersive term determined by the mesostructure and a nonlinear term derived using Hugoniot curves of components.

Nanosecond repetitively pulsed discharges in air at atmospheric pressure—the spark regime

NASA Astrophysics Data System (ADS)

Pai, David Z.; Lacoste, Deanna A.; Laux, Christophe O.

2010-12-01

Nanosecond repetitively pulsed (NRP) spark discharges have been studied in atmospheric pressure air preheated to 1000 K. Measurements of spark initiation and stability, plasma dynamics, gas temperature and current-voltage characteristics of the spark regime are presented. Using 10 ns pulses applied repetitively at 30 kHz, we find that 2-400 pulses are required to initiate the spark, depending on the applied voltage. Furthermore, about 30-50 pulses are required for the spark discharge to reach steady state, following initiation. Based on space- and time-resolved optical emission spectroscopy, the spark discharge in steady state is found to ignite homogeneously in the discharge gap, without evidence of an initial streamer. Using measured emission from the N2 (C-B) 0-0 band, it is found that the gas temperature rises by several thousand Kelvin in the span of about 30 ns following the application of the high-voltage pulse. Current-voltage measurements show that up to 20-40 A of conduction current is generated, which corresponds to an electron number density of up to 1015 cm-3 towards the end of the high-voltage pulse. The discharge dynamics, gas temperature and electron number density are consistent with a streamer-less spark that develops homogeneously through avalanche ionization in volume. This occurs because the pre-ionization electron number density of about 1011 cm-3 produced by the high frequency train of pulses is above the critical density for streamer-less discharge development, which is shown to be about 108 cm-3.

Identification and classification of transient pulses observed in magnetometer array data by time-domain principal component analysis filtering

NASA Astrophysics Data System (ADS)

Kappler, Karl N.; Schneider, Daniel D.; MacLean, Laura S.; Bleier, Thomas E.

2017-08-01

A method for identification of pulsations in time series of magnetic field data which are simultaneously present in multiple channels of data at one or more sensor locations is described. Candidate pulsations of interest are first identified in geomagnetic time series by inspection. Time series of these "training events" are represented in matrix form and transpose-multiplied to generate time-domain covariance matrices. The ranked eigenvectors of this matrix are stored as a feature of the pulsation. In the second stage of the algorithm, a sliding window (approximately the width of the training event) is moved across the vector-valued time-series comprising the channels on which the training event was observed. At each window position, the data covariance matrix and associated eigenvectors are calculated. We compare the orientation of the dominant eigenvectors of the training data to those from the windowed data and flag windows where the dominant eigenvectors directions are similar. This was successful in automatically identifying pulses which share polarization and appear to be from the same source process. We apply the method to a case study of continuously sampled (50 Hz) data from six observatories, each equipped with three-component induction coil magnetometers. We examine a 90-day interval of data associated with a cluster of four observatories located within 50 km of Napa, California, together with two remote reference stations-one 100 km to the north of the cluster and the other 350 km south. When the training data contains signals present in the remote reference observatories, we are reliably able to identify and extract global geomagnetic signals such as solar-generated noise. When training data contains pulsations only observed in the cluster of local observatories, we identify several types of non-plane wave signals having similar polarization.

Primary reaction control system/remote manipulator system interaction with loaded arm. Space shuttle engineering and operations support

NASA Technical Reports Server (NTRS)

Taylor, E. C.; Davis, J. D.

1978-01-01

A study of the interaction between the orbiter primary reaction control system (PRCS) and the remote manipulator system (RMS) with a loaded arm is documented. This analysis was performed with the Payload Deployment and Retrieval Systems Simulation (PDRSS) program with the passive arm bending option. The passive-arm model simulates the arm as massless elastic links with locked joints. The study was divided into two parts. The first part was the evaluation of the response of the arm to step inputs (i.e. constant jet torques) about each of the orbiter body axes. The second part of the study was the evaluation of the response of the arm to minimum impulse primary RCS jet firings with both single pulse and pulse train inputs.

Laser damage resistant nematic liquid crystal cell

NASA Astrophysics Data System (ADS)

Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Soms, L.; Marczak, J.; Nowinowski-Kruszelnicki, E.; Perkowski, P.; Kedzierski, J.; Miszczyk, E.; Olifierczuk, M.; Morawiak, P.; Mazur, R.

2013-08-01

There exists a problem in diagnostics of a dense plasma (so-called Thomson diagnostics). For this purpose, the plasma is illuminated by series of high energy laser pulses. Such pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along an exactly the same optical path. In this case, the energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, several independent lasers have to be used. To form optical path with λ = 1.064 μm and absolute value of the energy of laser pulse through of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell (NLCC) of type LCNP2 with switching on time τON smaller than 5 μs might be applied. High laser damage resistance of NLCC and short τON can be fulfilled by preparation of liquid crystal cells with Liquid Crystal Mixture (LCM), well tuned to twisted nematic electro-optical effect, and well tuned all optical interfaces (Air - Antireflection - Quartz Plate - Electrode - Blocking Film - Aligning Layer - LCM - Aligning Layer - Blocking Film - Electrode - Quartz Plate - Antireflection - Air). In such LCNP2 cell, the transmission is higher than 97% at λ = 1.064 μm, as it is presented by Gooch and Tarry [J. Phys. D: Appl. Phys. 8, 1575 (1975)]. The safe laser density energy is about 0.6 J/cm2 for a train of laser pulses (λ = 1.064 μm, pulse duration 10 ns FWHM, pulse repetition rate 100 pps, train duration 10 s), so the area of liquid crystal cell tolerating 3 J through it shall be as large as 5 cm2. Due to the presence of two blocking film layers between electrodes, LCNP2 can be driven by high voltages. Switching on time smaller than τON = 5 μs was obtained under 200 V switching voltage.

Extraocular spectral photosensitivity in the tentacles of Hydra vulgaris.

PubMed

Guertin, S; Kass-Simon, G

2015-06-01

Previous electrophysiological studies on the cnidarian Hydra vulgaris have shown that hydra have a highly developed and specific photoresponse despite their lack of any structure recognizable as a traditional photoreceptor. In an effort to identify the site of hydra's photoreceptors, we recorded extracellularly from single excised tentacles and from ablated hypostomes lacking tentacles in absolute darkness and during exposure to light of various wavelengths. During recording, after an initial period of absolute darkness, tentacles or hypostomes were exposed to light from 450nm to 600nm, red, and white light. Exposure to light caused a change in the pattern and frequency of impulses in the tentacles that varied with color. The number of large tentacle pulses (TPs) increased at 550 and 600nm relative to darkness, whereas the number of small tentacle pulses (STPs) tended to decrease in 500nm light. Impulse frequency was significantly different among the different wavelengths. In addition to bursts of tentacle contraction pulses, long trains of pulses were observed. A change in lighting caused a switch from bursting to trains or vice versa. In contrast to excised tentacles, no change in electrical activity was seen in ablated hypostomes at any of the wavelengths relative to each other or relative to darkness. These results indicate that isolated tentacles can distinguish among and respond to various colors across the visible spectrum and suggest that electromagnetic information is transmitted from the tentacles to the hypostome where it may be integrated by the hypostomal nervous system, ultimately contributing to hydra's photoreceptive behavior. Copyright © 2015 Elsevier Inc. All rights reserved.

Predictions of the Contribution of HCN Half-Maximal Activation Potential Heterogeneity to Variability in Intrinsic Adaptation of Spiral Ganglion Neurons.

PubMed

Boulet, Jason; Bruce, Ian C

2017-04-01

Spiral ganglion neurons (SGNs) exhibit a wide range in their strength of intrinsic adaptation on a timescale of 10s to 100s of milliseconds in response to electrical stimulation from a cochlear implant (CI). The purpose of this study was to determine how much of that variability could be caused by the heterogeneity in half-maximal activation potentials of hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels, which are known to produce intrinsic adaptation. In this study, a computational membrane model of cat type I SGN was developed based on the Hodgkin-Huxley model plus HCN and low-threshold potassium (KLT) conductances in which the half-maximal activation potential of the HCN channel was varied and the response of the SGN to pulse train and paired-pulse stimulation was simulated. Physiologically plausible variation of HCN half-maximal activation potentials could indeed determine the range of adaptation on the timescale of 10s to 100s of milliseconds and recovery from adaptation seen in the physiological data while maintaining refractoriness within physiological bounds. This computational model demonstrates that HCN channels may play an important role in regulating the degree of adaptation in response to pulse train stimulation and therefore contribute to variable constraints on acoustic information coding by CIs. This finding has broad implications for CI stimulation paradigms in that cell-to-cell variation of HCN channel properties are likely to significantly alter SGN excitability and therefore auditory perception.

Theoretical and experimental investigations of coincidences in Poisson distributed pulse trains and spectral distortion caused by pulse pileup

NASA Astrophysics Data System (ADS)

Bristow, Quentin

1990-03-01

The occurrence rates of pulse strings, or sequences of pulses with interarrival times less than the resolving time of the pulse-height analysis system used to acquire spectra, are derived from theoretical considerations. Logic circuits were devised to make experimental measurements of multiple pulse string occurrence rates in the output from a scintillation detector over a wide range of count rates. Markov process theory was used to predict state transition rates in the logic circuits, enabling the experimental data to be checked rigorously for conformity with those predicted for a Poisson distribution. No fundamental discrepancies were observed. Monte Carlo simulations, incorporating criteria for pulse pileup inherent in the operation of modern analog to digital converters, were used to generate pileup spectra due to coincidences between two pulses (first order pileup) and three pulses (second order pileup) for different semi-Gaussian pulse shapes. Coincidences between pulses in a single channel produced a basic probability density function spectrum. The use of a flat spectrum showed the first order pileup distorted the spectrum to a linear ramp with a pileup tail. A correction algorithm was successfully applied to correct entire spectra (simulated and real) for first and second order pileups.

Pulse analysis of acoustic emission signals

NASA Technical Reports Server (NTRS)

Houghton, J. R.; Packman, P. F.

1977-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameter values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emission associated with (a) crack propagation, (b) ball dropping on a plate, (c) spark discharge, and (d) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train is shown to be the region in which the significant signatures of the acoustic emission event are to be found.

Pulse analysis of acoustic emission signals

NASA Technical Reports Server (NTRS)

Houghton, J. R.; Packman, P. F.

1977-01-01

A method for the signature analysis of pulses in the frequency domain and the time domain is presented. Fourier spectrum, Fourier transfer function, shock spectrum and shock spectrum ratio were examined in the frequency domain analysis, and pulse shape deconvolution was developed for use in the time domain analysis. Comparisons of the relative performance of each analysis technique are made for the characterization of acoustic emission pulses recorded by a measuring system. To demonstrate the relative sensitivity of each of the methods to small changes in the pulse shape, signatures of computer modeled systems with analytical pulses are presented. Optimization techniques are developed and used to indicate the best design parameters values for deconvolution of the pulse shape. Several experiments are presented that test the pulse signature analysis methods on different acoustic emission sources. These include acoustic emissions associated with: (1) crack propagation, (2) ball dropping on a plate, (3) spark discharge and (4) defective and good ball bearings. Deconvolution of the first few micro-seconds of the pulse train are shown to be the region in which the significant signatures of the acoustic emission event are to be found.

A randomized study of the effects of exercise training on patients with atrial fibrillation.

PubMed

Osbak, Philip Samuel; Mourier, Malene; Kjaer, Andreas; Henriksen, Jens Henrik; Kofoed, Klaus Fuglsang; Jensen, Gorm Boje

2011-12-01

Exercise training is beneficial in ischemic and congestive heart disease. However, the effect on atrial fibrillation (AF) is unknown. Forty-nine patients with permanent AF (age [mean ± SD], 70.2 ± 7.8 years; male-to-female ratio, 0.75; body mass index [mean ± SD], 29.7 ± 4.3 kg/m(2)) were randomized to 12-week aerobic exercise training or a control group. Exercise capacity, 6-minute walk test (6MWT), cardiac output, quality of life, and natriuretic peptides were measured. Cardiac output was measured at rest and during ergometer testing, and atrial natriuretic peptide and N-terminal pro-B-type natriuretic peptide were measured before and after the training period. Quality of life was evaluated using the Short-Form 36 and Minnesota Living With Heart Failure (MLHF-Q) questionnaires. Improved exercise capacity and 6MWT were observed in the active patients (P < .001), and at study end, there was a significant difference between the active patients and the controls (P = .002). Resting pulse decreased in the active patients (94.8 ± 22.4 to 86.3 ± 22.5 beats/min, P = .049) but remained unchanged in the controls. Cardiac output was unchanged from baseline to end-of-study period. The MLHF-Q score improved in the active group (21.1 ± 18.0 vs 15.4 ± 17.5, P = .03). Active patients showed progress in 3 of the 8 Short-Form 36 subscales: physical functioning (P = .02), general health perceptions (P = .001), and vitality (P = .02). Natriuretic peptides were unchanged. Twelve weeks of exercise training increased exercise capacity and 6MWT and decreased resting pulse rate significantly in patients with AF. Overall quality of life increased significantly as measured by the cardiology-related MLHF-Q. Cardiac output and natriuretic peptides were unchanged in both groups. Copyright © 2011 Mosby, Inc. All rights reserved.

New Techniques for Investigating Properties of Energetic Solids at High Static and Dynamic Pressures.

DTIC Science & Technology

1976-09-01

fluid. For optical measurements in the regions of extremely high absorption ( lOs — io6 cm~~) thin films are required with a thickness of 500—5000L The top...round trip in the cavity. The result is a series of extremely narrow pulses, each pulse a few picoseconds ( lO ~~2 seconds) in duration and separated...electronic pulsar and electro—optic selection elements, it is possible to extract a single picosecond pulse from the train. This is I achieved by placing a

Laboratory-Model Integrated-System FARAD Thruster

NASA Technical Reports Server (NTRS)

Polzin, K.A.; Best, S.; Miller, R.; Rose, M.F.; Owens, T.

2008-01-01

Pulsed inductive plasma accelerators are spacecraft propulsion devices in which energy is stored in a capacitor and then discharged through an inductive coil. The device is electrodeless, inducing a plasma current sheet in propellant located near the face of the coil. The propellant is accelerated and expelled at a high exhaust velocity (order of 10 km/s) through the interaction of the plasma current with an induced magnetic field. The Faraday Accelerator with RF-Assisted Discharge (FARAD) thruster [1,2] is a type of pulsed inductive plasma accelerator in which the plasma is preionized by a mechanism separate from that used to form the current sheet and accelerate the gas. Employing a separate preionization mechanism in this manner allows for the formation of an inductive current sheet at much lower discharge energies and voltages than those found in previous pulsed inductive accelerators like the Pulsed Inductive Thruster (PIT). In a previous paper [3], the authors presented a basic design for a 100 J/pulse FARAD laboratory-version thruster. The design was based upon guidelines and performance scaling parameters presented in Refs. [4, 5]. In this paper, we expand upon the design presented in Ref. [3] by presenting a fully-assembled and operational FARAD laboratory-model thruster and addressing system and subsystem-integration issues (concerning mass injection, preionization, and acceleration) that arose during assembly. Experimental data quantifying the operation of this thruster, including detailed internal plasma measurements, are presented by the authors in a companion paper [6]. The thruster operates by first injecting neutral gas over the face of a flat, inductive acceleration coil and at some later time preionizing the gas. Once the gas is preionized current is passed through the acceleration coil, inducing a plasma current sheet in the propellant that is accelerated away from the coil through electromagnetic interaction with the time-varying magnetic field. Neutral gas is injected over the face of the acceleration coil through a fast-acting valve that feeds a central distribution manifold. The thruster is designed to preionize the gas using an RF-frequency ringing signal produced by a discharging Vector Inversion Generator (VIG). The acceleration stage consists of a multiple-turn, multiple-strand spiral induction coil (see Fig. 1, left panel) and is designed for operation at discharge energies on the order of 100 J/pulse. Several different pulsed power train modules can be used to drive current through the acceleration coil. One such power train is based upon the Bernardes and Merryman circuit topology, which restricts voltage reversal on the capacitor banks and can be clamped to eliminate current reversal in the coil. A second option is a pulse-compression-ring power train (see Fig. 1, right panel), which takesa temporally broad, low current pulse and transforms it into a short, high current pulse.

Laser-assisted hair removal for facial hirsutism in women: A review of evidence.

PubMed

Lee, Chun-Man

2018-06-01

Poly cystic ovarian syndrome (PCOS) has been described as the common diagnosis for hirsutism in women. Facial hirsutism is by far the most distressing symptom of hyperandrogenism in women with PCOS. A statistically significant improvement in psychological well-being has been reported in patients with PCOS allocated for laser-assisted hair removal. The theory of selective photothermolysis has revolutionized laser hair removal in that it is effective and safe, when operated by sufficiently trained and experienced professionals. Long-pulsed ruby (694 nm), long-pulsed alexandrite (755 nm), diode (800-980 nm), and long-pulsed Nd:YAG (1064 nm) are commercially available laser devices for hair removal most widely studied. This article will introduce the fundamentals and mechanism of action of lasers in hair removal, in a contemporary literature review looking at medium to long term efficacy and safety profiles of various laser hair removal modalities most widely commercially available to date.

Passive mode-locking of a diode-pumped Nd:YVO(4) laser by intracavity SHG in PPKTP.

PubMed

Iliev, Hristo; Chuchumishev, Danail; Buchvarov, Ivan; Petrov, Valentin

2010-03-15

Experimental results on passive mode-locking of a Nd:YVO(4) laser using intracavity frequency doubling in periodically poled KTP (PPKTP) crystal are reported. Both, negative cascaded chi((2)) lensing and frequency doubling nonlinear mirror (FDNLM) are exploited for the laser mode-locking. The FDNLM based on intensity dependent reflection in the laser cavity ensures self-starting and self-sustaining mode-locking while the cascaded chi((2)) lens process contributes to substantial pulse shortening. This hybrid technique enables generation of stable trains of pulses at high-average output power with several picoseconds pulse width. The pulse repetition rate of the laser is 117 MHz with average output power ranging from 0.5 to 3.1 W and pulse duration from 2.9 to 5.2 ps.

Optimization of Pulsed-DEER Measurements for Gd-Based Labels: Choice of Operational Frequencies, Pulse Durations and Positions, and Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raitsimring, A.; Astashkin, A. V.; Enemark, J. H.

2012-12-29

In this work, the experimental conditions and parameters necessary to optimize the long-distance (≥ 60 Å) Double Electron-Electron Resonance (DEER) measurements of biomacromolecules labeled with Gd(III) tags are analyzed. The specific parameters discussed are the temperature, microwave band, the separation between the pumping and observation frequencies, pulse train repetition rate, pulse durations and pulse positioning in the electron paramagnetic resonance spectrum. It was found that: (i) in optimized DEER measurements, the observation pulses have to be applied at the maximum of the EPR spectrum; (ii) the optimal temperature range for Ka-band measurements is 14-17 K, while in W-band the optimalmore » temperatures are between 6-9 K; (iii) W-band is preferable to Ka-band for DEER measurements. Recent achievements and the conditions necessary for short-distance measurements (<15 Å) are also briefly discussed.« less

Multi-mJ energy extraction using Yb-fiber based coherent pulse stacking amplification of fs pulses (Conference Presentation)

NASA Astrophysics Data System (ADS)

Ruppe, John M.; Pei, Hanzhang; Chen, Siyun; Sheikhsofla, Morteza; Wilcox, Russell B.; Nees, John A.; Galvanauskas, Almantas

2017-03-01

We report multi-mJ energy (>5mJ) extraction from femtosecond-pulse Yb-doped fiber CPA using coherent pulse stacking amplification (CPSA) technique. This high energy extraction has been enabled by amplifying 10's of nanosecond long pulse sequence, and by using 85-µm core Yb-doped CCC fiber based power amplification stage. The CPSA system consists of 1-GHz repetition rate mode-locked fiber oscillator, followed by a pair of fast phase and amplitude electro-optic modulators, a diffraction-grating based pulse stretcher, a fiber amplifier chain, a GTI-cavity based pulse stacker, and a diffraction grating pulse compressor. Electro-optic modulators are used to carve out from the 1-GHz mode-locked pulse train an amplitude and phase modulated pulse burst, which after stretching and amplification, becomes equal-amplitude pulse burst consisting of 27 stretched pulses, each approximately 1-ns long. Initial pulse-burst shaping accounts for the strong amplifier saturation effects, so that it is compensated at the power amplifier output. This 27-pulse burst is then coherently stacked into a single pulse using a multiplexed sequence of 5 GTI cavities. The compact-footprint 4+1 multiplexed pulse stacker consists of 4 cavities having rountrip of 1 ns, and one Herriott-cell folded cavity - with 9ns roundtrip. After stacking, stretched pulses are compressed down to the bandwidth-limited 300 fs duration using a standard diffraction-grating pulse compressor.

Improving Patient Safety through Simulation Training in Anesthesiology: Where Are We?

PubMed Central

2016-01-01

There have been colossal technological advances in the use of simulation in anesthesiology in the past 2 decades. Over the years, the use of simulation has gone from low fidelity to high fidelity models that mimic human responses in a startlingly realistic manner, extremely life-like mannequin that breathes, generates E.K.G, and has pulses, heart sounds, and an airway that can be programmed for different degrees of obstruction. Simulation in anesthesiology is no longer a research fascination but an integral part of resident education and one of ACGME requirements for resident graduation. Simulation training has been objectively shown to increase the skill-set of anesthesiologists. Anesthesiology is leading the movement in patient safety. It is rational to assume a relationship between simulation training and patient safety. Nevertheless there has not been a demonstrable improvement in patient outcomes with simulation training. Larger prospective studies that evaluate the improvement in patient outcomes are needed to justify the integration of simulation training in resident education but ample number of studies in the past 5 years do show a definite benefit of using simulation in anesthesiology training. This paper gives a brief overview of the history and evolution of use of simulation in anesthesiology and highlights some of the more recent studies that have advanced simulation-based training. PMID:26949389

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

PubMed Central

Shea-Brown, Eric; Rubinstein, Jay T.

2010-01-01

Cochlear implant speech processors stimulate the auditory nerve by delivering amplitude-modulated electrical pulse trains to intracochlear electrodes. Studying how auditory nerve cells encode modulation information is of fundamental importance, therefore, to understanding cochlear implant function and improving speech perception in cochlear implant users. In this paper, we analyze simulated responses of the auditory nerve to amplitude-modulated cochlear implant stimuli using a point process model. First, we quantify the information encoded in the spike trains by testing an ideal observer’s ability to detect amplitude modulation in a two-alternative forced-choice task. We vary the amount of information available to the observer to probe how spike timing and averaged firing rate encode modulation. Second, we construct a neural decoding method that predicts several qualitative trends observed in psychophysical tests of amplitude modulation detection in cochlear implant listeners. We find that modulation information is primarily available in the sequence of spike times. The performance of an ideal observer, however, is inconsistent with observed trends in psychophysical data. Using a neural decoding method that jitters spike times to degrade its temporal resolution and then computes a common measure of phase locking from spike trains of a heterogeneous population of model nerve cells, we predict the correct qualitative dependence of modulation detection thresholds on modulation frequency and stimulus level. The decoder does not predict the observed loss of modulation sensitivity at high carrier pulse rates, but this framework can be applied to future models that better represent auditory nerve responses to high carrier pulse rate stimuli. The supplemental material of this article contains the article’s data in an active, re-usable format. PMID:20177761

15 ps quasi-continuously pumped passively mode-locked highly doped Nd:YAG laser in bounce geometry

NASA Astrophysics Data System (ADS)

Jelínek, M., Jr.; Kubeček, V.

2011-09-01

A semiconductor saturable absorber mirror mode-locking of a quasi-continuously pumped laser based on 2.4 at.% Nd:YAG slab in a bounce geometry was demonstrated and investigated. Output mode-locked and Q-switched train containing 15 pulses with total energy of 500 μJ was generated directly from the oscillator. The measured 15 ps pulse duration and excellent temporal stability ±2 ps are the best values for pure passively mode-locked and Q-switched Nd:YAG laser with the pulse pumping. Furthermore, using the cavity dumping technique, single 19 ps pulse with energy of 25 μJ was extracted directly from the oscillator.

Multimodal fiber source for nonlinear microscopy based on a dissipative soliton laser

PubMed Central

Lamb, Erin S.; Wise, Frank W.

2015-01-01

Recent developments in high energy femtosecond fiber lasers have enabled robust and lower-cost sources for multiphoton-fluorescence and harmonic-generation imaging. However, picosecond pulses are better suited for Raman scattering microscopy, so the ideal multimodal source for nonlinear microcopy needs to provide both durations. Here we present spectral compression of a high-power femtosecond fiber laser as a route to producing transform-limited picosecond pulses. These pulses pump a fiber optical parametric oscillator to yield a robust fiber source capable of providing the synchronized picosecond pulse trains needed for Raman scattering microscopy. Thus, this system can be used as a multimodal platform for nonlinear microscopy techniques. PMID:26417497

Effects of training and simulated combat stress on leg tourniquet application accuracy, time, and effectiveness.

PubMed

Schreckengaust, Richard; Littlejohn, Lanny; Zarow, Gregory J

2014-02-01

The lower extremity tourniquet failure rate remains significantly higher in combat than in preclinical testing, so we hypothesized that tourniquet placement accuracy, speed, and effectiveness would improve during training and decline during simulated combat. Navy Hospital Corpsman (N = 89), enrolled in a Tactical Combat Casualty Care training course in preparation for deployment, applied Combat Application Tourniquet (CAT) and the Special Operations Forces Tactical Tourniquet (SOFT-T) on day 1 and day 4 of classroom training, then under simulated combat, wherein participants ran an obstacle course to apply a tourniquet while wearing full body armor and avoiding simulated small arms fire (paint balls). Application time and pulse elimination effectiveness improved day 1 to day 4 (p < 0.005). Under simulated combat, application time slowed significantly (p < 0.001), whereas accuracy and effectiveness declined slightly. Pulse elimination was poor for CAT (25% failure) and SOFT-T (60% failure) even in classroom conditions following training. CAT was more quickly applied (p < 0.005) and more effective (p < 0.002) than SOFT-T. Training fostered fast and effective application of leg tourniquets while performance declined under simulated combat. The inherent efficacy of tourniquet products contributes to high failure rates under combat conditions, pointing to the need for superior tourniquets and for rigorous deployment preparation training in simulated combat scenarios. Reprint & Copyright © 2014 Association of Military Surgeons of the U.S.

Calibrating and training of neutron based NSA techniques with less SNM standards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geist, William H; Swinhoe, Martyn T; Bracken, David S

2010-01-01

Accessing special nuclear material (SNM) standards for the calibration of and training on nondestructive assay (NDA) instruments has become increasingly difficult in light of enhanced safeguards and security regulations. Limited or nonexistent access to SNM has affected neutron based NDA techniques more than gamma ray techniques because the effects of multiplication require a range of masses to accurately measure the detector response. Neutron based NDA techniques can also be greatly affected by the matrix and impurity characteristics of the item. The safeguards community has been developing techniques for calibrating instrumentation and training personnel with dwindling numbers of SNM standards. Montemore » Carlo methods have become increasingly important for design and calibration of instrumentation. Monte Carlo techniques have the ability to accurately predict the detector response for passive techniques. The Monte Carlo results are usually benchmarked to neutron source measurements such as californium. For active techniques, the modeling becomes more difficult because of the interaction of the interrogation source with the detector and nuclear material; and the results cannot be simply benchmarked with neutron sources. A Monte Carlo calculated calibration curve for a training course in Indonesia of material test reactor (MTR) fuel elements assayed with an active well coincidence counter (AWCC) will be presented as an example. Performing training activities with reduced amounts of nuclear material makes it difficult to demonstrate how the multiplication and matrix properties of the item affects the detector response and limits the knowledge that can be obtained with hands-on training. A neutron pulse simulator (NPS) has been developed that can produce a pulse stream representative of a real pulse stream output from a detector measuring SNM. The NPS has been used by the International Atomic Energy Agency (IAEA) for detector testing and training applications at the Agency due to the lack of appropriate SNM standards. This paper will address the effect of reduced access to SNM for calibration and training of neutron NDA applications along with the advantages and disadvantages of some solutions that do not use standards, such as the Monte Carlo techniques and the NPS.« less

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers

PubMed Central

Yao, B. C.; Rao, Y. J.; Wang, Z. N.; Wu, Y.; Zhou, J. H.; Wu, H.; Fan, M. Q.; Cao, X. L.; Zhang, W. L.; Chen, Y. F.; Li, Y. R.; Churkin, D.; Turitsyn, S.; Wong, C. W.

2015-01-01

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses. PMID:26687730

Graphene based widely-tunable and singly-polarized pulse generation with random fiber lasers.

PubMed

Yao, B C; Rao, Y J; Wang, Z N; Wu, Y; Zhou, J H; Wu, H; Fan, M Q; Cao, X L; Zhang, W L; Chen, Y F; Li, Y R; Churkin, D; Turitsyn, S; Wong, C W

2015-12-21

Pulse generation often requires a stabilized cavity and its corresponding mode structure for initial phase-locking. Contrastingly, modeless cavity-free random lasers provide new possibilities for high quantum efficiency lasing that could potentially be widely tunable spectrally and temporally. Pulse generation in random lasers, however, has remained elusive since the discovery of modeless gain lasing. Here we report coherent pulse generation with modeless random lasers based on the unique polarization selectivity and broadband saturable absorption of monolayer graphene. Simultaneous temporal compression of cavity-free pulses are observed with such a polarization modulation, along with a broadly-tunable pulsewidth across two orders of magnitude down to 900 ps, a broadly-tunable repetition rate across three orders of magnitude up to 3 MHz, and a singly-polarized pulse train at 41 dB extinction ratio, about an order of magnitude larger than conventional pulsed fiber lasers. Moreover, our graphene-based pulse formation also demonstrates robust pulse-to-pulse stability and wide-wavelength operation due to the cavity-less feature. Such a graphene-based architecture not only provides a tunable pulsed random laser for fiber-optic sensing, speckle-free imaging, and laser-material processing, but also a new way for the non-random CW fiber lasers to generate widely tunable and singly-polarized pulses.

Repetitive Transcranial Magnetic Stimulator with Controllable Pulse Parameters

PubMed Central

Peterchev, Angel V; Murphy, David L; Lisanby, Sarah H

2013-01-01

The characteristics of transcranial magnetic stimulation (TMS) pulses influence the physiological effect of TMS. However, available TMS devices allow very limited adjustment of the pulse parameters. We describe a novel TMS device that uses a circuit topology incorporating two energy storage capacitors and two insulated-gate bipolar transistor (IGBT) modules to generate near-rectangular electric field pulses with adjustable number, polarity, duration, and amplitude of the pulse phases. This controllable pulse parameter TMS (cTMS) device can induce electric field pulses with phase widths of 10–310 μs and positive/negative phase amplitude ratio of 1–56. Compared to conventional monophasic and biphasic TMS, cTMS reduces energy dissipation by up to 82% and 57%, and decreases coil heating by up to 33% and 41%, respectively. We demonstrate repetitive TMS trains of 3,000 pulses at frequencies up to 50 Hz with electric field pulse amplitude and width variability less than the measurement resolution (1.7% and 1%, respectively). Offering flexible pulse parameter adjustment and reduced power consumption and coil heating, cTMS enhances existing TMS paradigms, enables novel research applications, and could lead to clinical applications with potentially enhanced potency. PMID:21540487

Noise reduction and control in mode-locked semiconductor diode lasers for use in next-generation all-optical analog-to-digital converters

NASA Astrophysics Data System (ADS)

DePriest, Christopher M.; Abeles, Joseph H.; Braun, Alan; Delfyett, Peter J., Jr.

2000-07-01

External-cavity, actively-modelocked semiconductor diode lasers (SDLs) have proven to be attractive candidates for forming the backbone of next-generation analog-to-digital converters (ADCs), which are currently being developed to sample signals at repetition rates exceeding several GHz with up to 12 bits of digital resolution. Modelocked SDLs are capable of producing waveform-sampling pulse trains with very low temporal jitter (phase noise) and very small fluctuations in pulse height (amplitude noise)--two basic conditions that must be met in order for high-speed ADCs to achieve projected design goals. Single-wavelength modelocked operation (at nominal repetition frequencies of 400 MHz) has produced pulse trains with very low amplitude noise (approximately 0.08%), and the implementation of a phase- locked-loop has been effective in reducing the system's low- frequency phase noise (RMS timing jitter for offset frequencies between 10 Hz and 10 kHz has been reduced from 240 fs to 27 fs).

Multi-color γ-rays from comb-like electron beams driven by incoherent stacks of laser pulses

NASA Astrophysics Data System (ADS)

Kalmykov, S. Y.; Davoine, X.; Ghebregziabher, I.; Shadwick, B. A.

2017-03-01

Trains of fs-length, GeV-scale electron bunches with controlled energy spacing and a 5-D brightness up to 1017 A/m2 may be produced in a mm-scale uniform plasma. The main element of the scheme is an incoherent stack of 10-TW-scale laser pulses of different colors, with mismatched focal spots, with the highest-frequency pulse advanced in time. While driving an electron density bubble, this stack remains almost proof against nonlinear red-shift and self-compression. As a consequence, the unwanted continuous injection of background electrons is minimized. Weak focusing of the trailing (lower-frequency) component of the stack enforces expansions and contractions of the bubble, inducing controlled periodic injection. The resulting train of electron bunches maintains exceptional quality while being accelerated beyond the energy limits predicted by accepted scalings. Inverse Thomson scattering from this comb-like beam generates a sequence of quasi-monochromatic, fs-length γ-ray beams, an asset for nuclear forensics and pump-probe experiments in dense plasmas.

Wave packet interferometry and quantum state reconstruction by acousto-optic phase modulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tekavec, Patrick F.; Dyke, Thomas R.; Marcus, Andrew H.

2006-11-21

Studies of wave packet dynamics often involve phase-selective measurements of coherent optical signals generated from sequences of ultrashort laser pulses. In wave packet interferometry (WPI), the separation between the temporal envelopes of the pulses must be precisely monitored or maintained. Here we introduce a new (and easy to implement) experimental scheme for phase-selective measurements that combines acousto-optic phase modulation with ultrashort laser excitation to produce an intensity-modulated fluorescence signal. Synchronous detection, with respect to an appropriately constructed reference, allows the signal to be simultaneously measured at two phases differing by 90 deg. Our method effectively decouples the relative temporal phasemore » from the pulse envelopes of a collinear train of optical pulse pairs. We thus achieve a robust and high signal-to-noise scheme for WPI applications, such as quantum state reconstruction and electronic spectroscopy. The validity of the method is demonstrated, and state reconstruction is performed, on a model quantum system - atomic Rb vapor. Moreover, we show that our measurements recover the correct separation between the absorptive and dispersive contributions to the system susceptibility.« less

Dynamics and detection of laser induced microbubbles in the retinal pigment epithelium (RPE)

NASA Astrophysics Data System (ADS)

Fritz, Andreas; Ptaszynski, Lars; Stoehr, Hardo; Brinkmann, Ralf

2007-07-01

Selective Retina Treatment (SRT) is a new method to treat eye diseases associated with disorders of the RPE. Selective RPE cell damage is achieved by applying a train of 1.7 μs laser pulses at 527 nm. The treatment of retinal diseases as e.g. diabetic maculopathy (DMP), is currently investigated within clinical studies, however 200 ns pulse durations are under investigation. Transient micro bubbles in the retinal pigment epithelium (RPE) are expected to be the origin of cell damage due to irradiation with laser pulses shorter than 50 μs. The bubbles emerge at the strongly absorbing RPE melanosomes. Cell membrane disruption caused by the transient associated volume increase is expected to be the origin of the angiographically observed RPE leakage. We investigate micro bubble formation and dynamics in porcine RPE using pulse durations of 150 ns. A laser interferometry system at 830 nm with the aim of an online dosimetry control for SRT was developed. Bubble formation was detected interferometrically and by fast flash photography. A correlation to cell damage observed with a vitality stain is found. A bubble detection algorithm is presented.

Physiological and performance changes from the addition of a sprint interval program to wrestling training.

PubMed

Farzad, Babak; Gharakhanlou, Reza; Agha-Alinejad, Hamid; Curby, David G; Bayati, Mahdi; Bahraminejad, Morteza; Mäestu, Jarek

2011-09-01

Increasing the level of physical fitness for competition is the primary goal of any conditioning program for wrestlers. Wrestlers often need to peak for competitions several times over an annual training cycle. Additionally, the scheduling of these competitions does not always match an ideal periodization plan and may require a modified training program to achieve a high level of competitive fitness in a short-time frame. The purpose of this study was to examine the effects of 4 weeks of sprint-interval training (SIT) program, on selected aerobic and anaerobic performance indices, and hormonal and hematological adaptations, when added to the traditional Iranian training of wrestlers in their preseason phase. Fifteen trained wrestlers were assigned to either an experimental (EXP) or a control (CON) group. Both groups followed a traditional preparation phase consisting of learning and drilling technique, live wrestling and weight training for 4 weeks. In addition, the EXP group performed a running-based SIT protocol. The SIT consisted of 6 35-m sprints at maximum effort with a 10-second recovery between each sprint. The SIT protocol was performed in 2 sessions per week, for the 4 weeks of the study. Before and after the 4-week training program, pre and posttesting was performed on each subject on the following: a graded exercise test (GXT) to determine VO(2)max, the velocity associated with V(2)max (νVO(2)max), maximal ventilation, and peak oxygen pulse; a time to exhaustion test (T(max)) at their νVO(2)max; and 4 successive Wingate tests with a 4-minute recovery between each trial for the determination of peak and mean power output (PPO, MPO). Resting blood samples were also collected at the beginning of each pre and posttesting period, before and after the 4-week training program. The EXP group showed significant improvements in VO(2)max (+5.4%), peak oxygen pulse (+7.7%) and T(max) (+32.2%) compared with pretesting. The EXP group produced significant increases in PPO and MPO during the Wingate testing compared with pretesting (p < 0.05). After the 4-week training program, total testosterone and the total testosterone/cortisol ratio increased significantly in the EXP group, whereas cortisol tended to decrease (p = 0.06). The current findings indicate that the addition of an SIT program with short recovery can improve both aerobic and anaerobic performances in trained wrestlers during the preseason phase. The hormonal changes seen suggest training-induced anabolic adaptations.

Educating the Educator: Use of Pulse Oximetry in Athletic Training

ERIC Educational Resources Information Center

Berry, David C.; Seitz, S. Robert

2012-01-01

The 5th edition of the "Athletic Training Education Competencies" expanded the scope of knowledge and skill set of entry-level athletic trainers related to the domain of "Acute Care of Injuries and Illnesses." One of these major changes includes the introduction of adjunct airway techniques, such as oropharyngeal and nasopharyngeal airways and…

A CMOS active pixel sensor for retinal stimulation

NASA Astrophysics Data System (ADS)

Prydderch, Mark L.; French, Marcus J.; Mathieson, Keith; Adams, Christopher; Gunning, Deborah; Laudanski, Jonathan; Morrison, James D.; Moodie, Alan R.; Sinclair, James

2006-02-01

Degenerative photoreceptor diseases, such as age-related macular degeneration and retinitis pigmentosa, are the most common causes of blindness in the western world. A potential cure is to use a microelectronic retinal prosthesis to provide electrical stimulation to the remaining healthy retinal cells. We describe a prototype CMOS Active Pixel Sensor capable of detecting a visual scene and translating it into a train of electrical pulses for stimulation of the retina. The sensor consists of a 10 x 10 array of 100 micron square pixels fabricated on a 0.35 micron CMOS process. Light incident upon each pixel is converted into output current pulse trains with a frequency related to the light intensity. These outputs are connected to a biocompatible microelectrode array for contact to the retinal cells. The flexible design allows experimentation with signal amplitudes and frequencies in order to determine the most appropriate stimulus for the retina. Neural processing in the retina can be studied by using the sensor in conjunction with a Field Programmable Gate Array (FPGA) programmed to behave as a neural network. The sensor has been integrated into a test system designed for studying retinal response. We present the most recent results obtained from this sensor.

Dynamic Rupture and Energy Partition in Models of Earthquake Faults

NASA Astrophysics Data System (ADS)

Shi, Z.; Needleman, A.; Ben-Zion, Y.

2006-12-01

We study properties of dynamic rupture and the partition of energy between radiation and dissipative mechanisms using 2D finite element calculations. The goal is to improve the understanding of these processes on faults at different evolutionary stages associated with different levels of geometrical complexity and possible presence of contrasting elastic properties across the fault. The initial calculations employ homogeneous media and a planar internal interface governed by a general rate- and state-dependent friction law that accounts for the gradual response of shear stress to abrupt changes of normal stress. Ruptures are initiated by gradually increasing the shear traction in a limited nucleation zone near the origin. By changing the rate dependency of the friction law and the size of the nucleation zone, we obtain four rupture modes: (i) supershear crack-like rupture; (ii) subshear crack-like rupture; (iii) subshear single pulse; and (iv) supershear train of pulses. Increasing the initial shear stress produces a transition from a subshear crack to a supershear crack, while increasing the rate dependency of the friction produces self-healing and the transition from a crack-like to a pulse mode of rupture. Properties of the nucleation process can strongly affect the rupture mode. In the cases examined, the total release of strain energy (over the same propagation distance) decreases following the order: supershear crack, subshear crack, train of pulses and single pulse. The ratio of the radiated kinetic energy to the energy dissipated in friction is about 5% for the supershear crack case and about 2% for the other three cases. Future work will involve similar calculations accounting for the generation of plastic strain in the bulk, the material contrast across the fault, and the addition of cohesive surfaces in the bulk to allow for the generation of new surfaces. The study may provide fundamental information on rupture processes in geologically-relevant circumstances and improve the understanding of physical limits on extreme ground motion. The results may be used to check assumptions made in observational works and may help to guide new observational research.

Temperature Insensitive and Radiation Hard Photonics

DTIC Science & Technology

2014-03-19

M. COOK , Lt Col, USAF Deputy Chief, Spacecraft Technology Division Space Vehicles Directorate This report is published in the interest of...Approved for Public Release; distribution is unlimited. ii LIST OF FIGURES Figure 1. OTDM Pulse Multiplexer for Increasing the Output Repetition Rate...QDMLL) for use in extreme environments where ionizing radiation is a substantial threat. Mode-Locked lasers generate a train of optical pulses that have

Efficient model for low-energy transverse beam dynamics in a nine-cell 1.3 GHz cavity

NASA Astrophysics Data System (ADS)

Hellert, Thorsten; Dohlus, Martin; Decking, Winfried

2017-10-01

FLASH and the European XFEL are SASE-FEL user facilities, at which superconducting TESLA cavities are operated in a pulsed mode to accelerate long bunch-trains. Several cavities are powered by one klystron. While the low-level rf system is able to stabilize the vector sum of the accelerating gradient of one rf station sufficiently, the rf parameters of individual cavities vary within the bunch-train. In correlation with misalignments, intrabunch-train trajectory variations are induced. An efficient model is developed to describe the effect at low beam energy, using numerically adjusted transfer matrices and discrete coupler kick coefficients, respectively. Comparison with start-to-end tracking and dedicated experiments at the FLASH injector will be shown. The short computation time of the derived model allows for comprehensive numerical studies on the impact of misalignments and variable rf parameters on the transverse intra-bunch-train beam stability at the injector module. Results from both, statistical multibunch performance studies and the deduction of misalignments from multibunch experiments are presented.

Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

NASA Astrophysics Data System (ADS)

Liu, Ya; Zhao, Xin; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

2016-09-01

Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses with four-fold difference in pulsewidths and tens of Hz repetition rate difference is observed. The coherence between these spectral-overlapped, picosecond and femtosecond pulses is further verified by the corresponding asynchronous cross-sampling and dual-comb spectroscopy measurements.

Ultrashort, high power, and ultralow noise mode-locked optical pulse generation using quantum-dot semiconductor lasers

NASA Astrophysics Data System (ADS)

Choi, Myoung-Taek

This dissertation explores various aspects and potential of optical pulse generation based on active, passive, and hybrid mode-locked quantum dot semiconductor lasers with target applications such as optical interconnect and high speed signal processing. Design guidelines are developed for the single mode operation with suppressed reflection from waveguide discontinuities. The device fabrication procedure is explained, followed by characteristics of FP laser, SOA, and monolithic two-section devices. Short pulse generation from an external cavity mode-locked QD two-section diode laser is studied. High quality, sub-picosecond (960 fs), high peak power (1.2 W) pulse trains are obtained. The sign and magnitude of pulse chirp were measured for the first time. The role of the self-phase modulation and the linewidth enhancement factor in QD mode-locked lasers is addressed. The noise performance of two-section mode-locked lasers and a SOA-based ring laser was investigated. Significant reduction of the timing jitter under hybrid mode-locked operation was achieved owing to more than one order of magnitude reduction of the linewidth in QD gain media. Ultralow phase noise performance (integrated timing jitter of a few fs at a 10 GHz repetition rate) was demonstrated from an actively mode-locked unidirectional ring laser. These results show that quantum dot mode-locked lasers are strong competitors to conventional semiconductor lasers in noise performance. Finally we demonstrated an opto-electronic oscillator (OEO) and coupled opto-electronic oscillators (COEO) which have the potential for both high purity microwave and low noise optical pulse generation. The phase noise of the COEO is measured by the photonic delay line frequency discriminator method. Based on this study we discuss the prospects of the COEO as a low noise optical pulse source.

A high pulse repetition frequency ultrasound system for the ex vivo measurement of mechanical properties of crystalline lenses with laser-induced microbubbles interrogated by acoustic radiation force.

PubMed

Yoon, Sangpil; Aglyamov, Salavat; Karpiouk, Andrei; Emelianov, Stanislav

2012-08-07

A high pulse repetition frequency ultrasound system for an ex vivo measurement of mechanical properties of an animal crystalline lens was developed and validated. We measured the bulk displacement of laser-induced microbubbles created at different positions within the lens using nanosecond laser pulses. An impulsive acoustic radiation force was applied to the microbubble, and spatio-temporal measurements of the microbubble displacement were assessed using a custom-made high pulse repetition frequency ultrasound system consisting of two 25 MHz focused ultrasound transducers. One of these transducers was used to emit a train of ultrasound pulses and another transducer was used to receive the ultrasound echoes reflected from the microbubble. The developed system was operating at 1 MHz pulse repetition frequency. Based on the measured motion of the microbubble, Young's moduli of surrounding tissue were reconstructed and the values were compared with those measured using the indentation test. Measured values of Young's moduli of four bovine lenses ranged from 2.6 ± 0.1 to 26 ± 1.4 kPa, and there was good agreement between the two methods. Therefore, our studies, utilizing the high pulse repetition frequency ultrasound system, suggest that the developed approach can be used to assess the mechanical properties of ex vivo crystalline lenses. Furthermore, the potential of the presented approach for in vivo measurements is discussed.

Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire—KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

NASA Astrophysics Data System (ADS)

Zvorykin, V. D.; Ionin, Andrei A.; Levchenko, A. O.; Mesyats, Gennadii A.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, Igor V.; Sunchugasheva, E. S.; Ustinovskii, N. N.; Shutov, A. V.

2013-04-01

The problem of the production of extended (~1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2-0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration (~100 ns), maintains the electron density at a level ne = (3-5) × 1014 cm—3 by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy (~0.5 eV) and a long lifetime (~1 ms), which are produced upon cessation of the laser pulse.

Heat pulse excitability of vestibular hair cells and afferent neurons

PubMed Central

Brichta, Alan M.; Tabatabaee, Hessam; Boutros, Peter J.; Ahn, JoongHo; Della Santina, Charles C.; Poppi, Lauren A.; Lim, Rebecca

2016-01-01

In the present study we combined electrophysiology with optical heat pulse stimuli to examine thermodynamics of membrane electrical excitability in mammalian vestibular hair cells and afferent neurons. We recorded whole cell currents in mammalian type II vestibular hair cells using an excised preparation (mouse) and action potentials (APs) in afferent neurons in vivo (chinchilla) in response to optical heat pulses applied to the crista (ΔT ≈ 0.25°C per pulse). Afferent spike trains evoked by heat pulse stimuli were diverse and included asynchronous inhibition, asynchronous excitation, and/or phase-locked APs synchronized to each infrared heat pulse. Thermal responses of membrane currents responsible for APs in ganglion neurons were strictly excitatory, with Q10 ≈ 2. In contrast, hair cells responded with a mix of excitatory and inhibitory currents. Excitatory hair cell membrane currents included a thermoelectric capacitive current proportional to the rate of temperature rise (dT/dt) and an inward conduction current driven by ΔT. An iberiotoxin-sensitive inhibitory conduction current was also evoked by ΔT, rising in <3 ms and decaying with a time constant of ∼24 ms. The inhibitory component dominated whole cell currents in 50% of hair cells at −68 mV and in 67% of hair cells at −60 mV. Responses were quantified and described on the basis of first principles of thermodynamics. Results identify key molecular targets underlying heat pulse excitability in vestibular sensory organs and provide quantitative methods for rational application of optical heat pulses to examine protein biophysics and manipulate cellular excitability. PMID:27226448

The Discrimination of Pitch in Pulse Trains and Speech

DTIC Science & Technology

1984-04-12

music from their corresponding abilities with the simpler sounds which could serve as the •’• components of the more complex ones (p. 175). Two...reported normal hearing. Previous researchers have found that, on tests of tone or melody-sequence perception, musically trained subjects perform better...than individuals who have not had musical training (e.g. Stucker, 1980; Raz and Brandt, 1977; Zatorre, 1979). For this reason, subjects were asked to

Performance enhancement of sub-nanosecond diode-pumped passively Q-switched Yb:YAG microchip laser with diamond surface cooling.

PubMed

Zhuang, W Z; Chen, Yi-Fan; Su, K W; Huang, K F; Chen, Y F

2012-09-24

We experimentally confirm that diamond surface cooling can significantly enhance the output performance of a sub-nanosecond diode-end-pumped passively Q-switched Yb:YAG laser. It is found that the pulse energy obtained with diamond cooling is approximately 1.5 times greater than that obtained without diamond cooling, where a Cr(4+):YAG absorber with the initial transmission of 84% is employed. Furthermore, the standard deviation of the pulse amplitude peak-to-peak fluctuation is found to be approximately 3 times lower than that measured without diamond cooling. Under a pump power of 3.9 W, the passively Q-switched Yb:YAG laser can generate a pulse train of 3.3 kHz repetition rate with a pulse energy of 287 μJ and with a pulse width of 650 ps.

One-year unsupervised individualized exercise training intervention enhances cardiorespiratory fitness but not muscle deoxygenation or glycemic control in adults with type 1 diabetes.

PubMed

Rissanen, Antti-Pekka E; Tikkanen, Heikki O; Koponen, Anne S; Aho, Jyrki M; Peltonen, Juha E

2018-04-01

Adaptations to long-term exercise training in type 1 diabetes are sparsely studied. We examined the effects of a 1-year individualized training intervention on cardiorespiratory fitness, exercise-induced active muscle deoxygenation, and glycemic control in adults with and without type 1 diabetes. Eight men with type 1 diabetes (T1D) and 8 healthy men (CON) matched for age, anthropometry, and peak pulmonary O 2 uptake, completed a 1-year individualized training intervention in an unsupervised real-world setting. Before and after the intervention, the subjects performed a maximal incremental cycling test, during which alveolar gas exchange (volume turbine and mass spectrometry) and relative concentration changes in active leg muscle deoxygenated (Δ[HHb]) and total (Δ[tHb]) hemoglobin (near-infrared spectroscopy) were monitored. Peak O 2 pulse, reflecting peak stroke volume, was calculated (peak pulmonary O 2 uptake/peak heart rate). Glycemic control (glycosylated hemoglobin A 1c (HbA 1c )) was evaluated. Both T1D and CON averagely performed 1 resistance-training and 3-4 endurance-training sessions per week (∼1 h/session at ∼moderate intensity). Training increased peak pulmonary O 2 uptake in T1D (p = 0.004) and CON (p = 0.045) (group × time p = 0.677). Peak O 2 pulse also rose in T1D (p = 0.032) and CON (p = 0.018) (group × time p = 0.880). Training increased leg Δ[HHb] at peak exercise in CON (p = 0.039) but not in T1D (group × time p = 0.052), while no changes in leg Δ[tHb] at any work rate were observed in either group (p > 0.05). HbA 1c retained unchanged in T1D (from 58 ± 10 to 59 ± 11 mmol/mol, p = 0.609). In conclusion, 1-year adherence to exercise training enhanced cardiorespiratory fitness similarly in T1D and CON but had no effect on active muscle deoxygenation or glycemic control in T1D.

Superconducting Qubit with Integrated Single Flux Quantum Controller Part II: Experimental Characterization

NASA Astrophysics Data System (ADS)

Leonard, Edward, Jr.; Beck, Matthew; Thorbeck, Ted; Zhu, Shaojiang; Howington, Caleb; Nelson, Jj; Plourde, Britton; McDermott, Robert

We describe the characterization of a single flux quantum (SFQ) pulse generator cofabricated with a superconducting quantum circuit on a single chip. Resonant trains of SFQ pulses are used to induce coherent qubit rotations on the Bloch sphere. We describe the SFQ drive characteristics of the qubit at the fundamental transition frequency and at subharmonics (ω01 / n , n = 2 , 3 , 4 , ⋯). We address the issue of quasiparticle poisoning due to the proximal SFQ pulse generator, and we characterize the fidelity of SFQ-based rotations using randomized benchmarking. Present address: IBM T.J. Watson Research Center.

Attosecond electron pulses for 4D diffraction and microscopy

PubMed Central

Baum, Peter; Zewail, Ahmed H.

2007-01-01

In this contribution, we consider the advancement of ultrafast electron diffraction and microscopy to cover the attosecond time domain. The concept is centered on the compression of femtosecond electron packets to trains of 15-attosecond pulses by the use of the ponderomotive force in synthesized gratings of optical fields. Such attosecond electron pulses are significantly shorter than those achievable with extreme UV light sources near 25 nm (≈50 eV) and have the potential for applications in the visualization of ultrafast electron dynamics, especially of atomic structures, clusters of atoms, and some materials. PMID:18000040

Repetitively pulsed TEA CO{sub 2} laser and its application for second harmonic generation in ZnGeP{sub 2} crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koval'chuk, L V; Grezev, A N; Niz'ev, V G

2015-10-31

Experimental results are presented on the development of a radiation source emitting at a wavelength of 4.775 μm with a pulse energy up to 50 mJ and an average power up to several watts in short pulse trains. A TEA CO{sub 2} laser and a nonlinear converter based on a ZnGeP{sub 2} crystal, which are specially designed for these experiments, are described. The main limitations of nonlinear conversion and possible ways to overcome these limitations are considered. (lasers)

Source-to-sensation level ratio of transmitted biosonar pulses in an echolocating false killer whale.

PubMed

Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

2006-07-01

Transmitted biosonar pulses, and the brain auditory evoked potentials (AEPs) associated with those pulses, were synchronously recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP amplitude was investigated as a function of the transmitted biosonar pulse source level. For that, a few thousand of the individual AEP records were sorted according to the spontaneously varied amplitude of synchronously recorded biosonar pulses. In each of the sorting bins (in 5-dB steps) AEP records were averaged to extract AEP from noise; AEP amplitude was plotted as a function of the biosonar pulse source level. For comparison, AEPs were recorded to external (in free field) sound pulses of a waveform and spectrum similar to those of the biosonar pulses; amplitude of these AEPs was plotted as a function of sound pressure level. A comparison of these two functions has shown that, depending on the presence or absence of a target, the sensitivity of the whale's hearing to its own transmitted biosonar pulses was 30 to 45 dB lower than might be expected in a free acoustic field.

Mode locking of a ring cavity semiconductor diode laser

NASA Astrophysics Data System (ADS)

Desbiens, Louis; Yesayan, Ararat; Piche, Michel

2000-12-01

We report new results on the generation and characterization of picosecond pulses from a self-mode-locked semiconductor diode laser. The active medium (InGaAs, 830-870 nm) is a semiconductor optical amplifier whose facets are cut at angle and AR coated. The amplifier is inserted in a three-minor ring cavity. Mode locking is purely passive; it takes place for specific alignment conditions. Trains of counterpropagating pulses are produced, with pulse duration varying from 1 .2 to 2 ps. The spectra of the counterpropagatmg pulses do not fully overlap; their central wavelengths differ by a few nm. The pulse repetition rate has been varied from 0.3 to 3 GHz. The pulses have been compressed to less than 500-fs duration with a grating pair. We discuss some of the potential physical mechanisms that could be involved in the dynamics of the mode-locked regime. Hysteresis in the LI curve has been observed. To characterize the pulses, we introduce the idea of a Pulse Quality Factor, where the pulse duration and spectral width are calculated from the second-order moments of the measured intensity autocorrelation and power spectral density.

Dynamics of Micropipette Vibration During Piezo-assisted Microinjection

NASA Astrophysics Data System (ADS)

Karzar-Jeddi, Mehdi; Olgac, Nejat; Fan, Tai-Hsi

Microinjection is a well-accepted method to introduce materials such as sperm, DNA materials, or nucleus into a living cell for biomedical applications. The conventional microinjection procedure consists of immobilizing the cell by applying suction through a holding pipette, and then an injecting micropipette penetrates through the cell membrane and introduces the materials into the cell. To assist the penetration process a piezo-generated pulse train is applied to the injecting pipette, which causes an undesirable lateral vibration at the injecting pipette tip. In this research we provide an analytical model to study the response of micropipette to the piezo-pulse train using the Duhamel integral method. Our results show that filling the micropipette tip with mercury causes a larger amplitude stroke vibration in micropipette tip than that of empty micropipette when it is submerged in the viscous medium surrounding the cell. The mercury introduced larger stroke vibration can cause a larger shear force and assist the penetration of micropipette through the cell membrane. This work is supported by NSF CBET-0828733 and NIH R24RR018934-01.

Rapid variability, dying pulse trains and black holes

NASA Technical Reports Server (NTRS)

Stoeger, W. R.

1980-01-01

After reviewing the general model and arguments by which rapid temporal variability and quasi-periodicities are considered indicative of a compact source's possible black hole character, the paper presents a scenario for 'dying pulse trains'. These originate inside the inner edge of accretion disks encircling black holes from accreting flares or other self-luminous entities executing their final few revolutions before reaching the event horizon. Confirmed detection of such phenomena with time scales in the range 0.01 (M/solar mass) to 0.5 (M/solar mass)ms, where M is the mass of the compact source, would provide much better support for its black hole candidacy. Variability on time-scales larger than this by itself places few constraints on the nature of the compact object.

Freeze frame analysis on high speed cinematography of Nd/YAG laser explosions in ocular tissues.

PubMed

Vernon, S A; Cheng, H

1986-05-01

High speed colour cinematography at 400 frames per second was used to photograph both single and train burst Nd/YAG laser applications in ox eyes at threshold energy levels. Measurements of the extent and speed of particle scatter and tissue distortion from the acoustic transient were made from a sequential freeze frame analysis of the films. Particles were observed to travel over 8 mm from the site of Nd/YAG application 20 milliseconds after a single pulse at initial speeds in excess of 20 km/h. The use of train bursts of pulses was seen to increase the number of particles scattered and project the wavefront of particles further from the point of laser application.

Freeze frame analysis on high speed cinematography of Nd/YAG laser explosions in ocular tissues.

PubMed Central

Vernon, S A; Cheng, H

1986-01-01

High speed colour cinematography at 400 frames per second was used to photograph both single and train burst Nd/YAG laser applications in ox eyes at threshold energy levels. Measurements of the extent and speed of particle scatter and tissue distortion from the acoustic transient were made from a sequential freeze frame analysis of the films. Particles were observed to travel over 8 mm from the site of Nd/YAG application 20 milliseconds after a single pulse at initial speeds in excess of 20 km/h. The use of train bursts of pulses was seen to increase the number of particles scattered and project the wavefront of particles further from the point of laser application. Images PMID:3754458

Control of broadband optically generated ultrasound pulses using binary amplitude holograms.

PubMed

Brown, Michael D; Jaros, Jiri; Cox, Ben T; Treeby, Bradley E

2016-04-01

In this work, the use of binary amplitude holography is investigated as a mechanism to focus broadband acoustic pulses generated by high peak-power pulsed lasers. Two algorithms are described for the calculation of the binary holograms; one using ray-tracing, and one using an optimization based on direct binary search. It is shown using numerical simulations that when a binary amplitude hologram is excited by a train of laser pulses at its design frequency, the acoustic field can be focused at a pre-determined distribution of points, including single and multiple focal points, and line and square foci. The numerical results are validated by acoustic field measurements from binary amplitude holograms, excited by a high peak-power laser.

Phase control of attosecond pulses in a train

NASA Astrophysics Data System (ADS)

Guo, Chen; Harth, Anne; Carlström, Stefanos; Cheng, Yu-Chen; Mikaelsson, Sara; Mårsell, Erik; Heyl, Christoph; Miranda, Miguel; Gisselbrecht, Mathieu; Gaarde, Mette B.; Schafer, Kenneth J.; Mikkelsen, Anders; Mauritsson, Johan; Arnold, Cord L.; L'Huillier, Anne

2018-02-01

Ultrafast processes in matter can be captured and even controlled by using sequences of few-cycle optical pulses, which need to be well characterized, both in amplitude and phase. The same degree of control has not yet been achieved for few-cycle extreme ultraviolet pulses generated by high-order harmonic generation (HHG) in gases, with duration in the attosecond range. Here, we show that by varying the spectral phase and carrier-envelope phase (CEP) of a high-repetition rate laser, using dispersion in glass, we achieve a high degree of control of the relative phase and CEP between consecutive attosecond pulses. The experimental results are supported by a detailed theoretical analysis based upon the semi-classical three-step model for HHG.

Hybrid mode-locked fiber ring laser using graphene and charcoal nanoparticles as saturable absorbers

NASA Astrophysics Data System (ADS)

Hu, Hongyu; Zhang, Xiang; Li, Wenbo; Dutta, Niloy K.

2016-05-01

A fiber ring laser which implements hybrid mode locking technique has been proposed and experimentally demonstrated to generate pulse train at 20 GHz repetition rate with ultrashort pulse width. Graphene and charcoal nano-particles acting as passive mode lockers are inserted into a rational harmonic mode-locked fiber laser to improve the performance. With graphene saturable absorbers, the pulse duration is shortened from 5.3 ps to 2.8 ps, and with charcoal nano-particles, it is shortened to 3.2 ps. The RF spectra show that supermode noise can be removed in the presence of the saturable absorbers. Numerical simulation of the pulse transmission has also been carried out, which shows good agreement with the experimental results.

Sensitivity enhancements in MQ-MAS NMR of spin-5/2 nuclei using modulated rf mixing pulses

NASA Astrophysics Data System (ADS)

Vosegaard, Thomas; Massiot, Dominique; Grandinetti, Philip J.

2000-08-01

An X- overlineX pulse train with stepped modulation frequency was employed to enhance the multiple-quantum to single-quantum coherence transfer in the mixing period of the multiple-quantum magic-angle spinning (MQ-MAS) experiment for spin I=5/2 nuclei. Two MQ-MAS pulse sequences employing this mixing scheme for the triple-to-single and quintuple-to-single quantum coherence transfers have been designed and their performance is demonstrated for 27Al on samples of NaSi 3AlO 8 and 9Al 2O 3·2B 2O 3 . Compared to the standard single-pulse mixing sequences, the sensitivity is approximately doubled in the present experiments.

In-vivo experimental evaluation of nonablative skin remodeling using a 1.54-μm laser with surface cooling

NASA Astrophysics Data System (ADS)

Mordon, Serge R.; Capon, Alexandre; Creusy, Collette; Fleurisse, Laurence; Buys, Bruno; Faucheux, Marc A.; Servell, Pascal

2000-05-01

Selective dermal remodeling using diode or 1.32 micrometer Nd:YAG lasers has been recently proposed for skin rejuvenation. This new technique consists in inducing collagen tightening and/or neocollagen synthesis without significant damage of the overlying epidermis. Such an approach requires (1) a cooling system in order to target dermal collagen with relatively good protection of the epidermal layer, (2) a specific wavelength for confining the thermal damage into the upper dermis (100 to 400 micrometer). Based on previous studies, demonstrating a better water absorption and a reduced melanin absorption at 1.54 micrometer compared to the 1.32 micrometer, this experimental study aimed to evaluate a new laser (co-doped Yb-Er:phosphate glass material, Aramis, Quantel-France) emitting at 1.54 micrometer. This laser was used in combination with the Dermacool system (Dermacool, Mableton, USA) in order to achieve epidermis cooling before, during and after irradiation. Male hairless rats were used for the study. Pulse train irradiation (1.1 J, 3 Hz, 30 pulses) and different cooling temperatures (+5 degree(s)C, 0 degree(s)C, -5 degree(s)C) were screened with clinical examination and histological evaluation at 1, 3, and 7 days after laser irradiation. The clinical effects showed that pulse train irradiation produced reproducible epidermal preservation and confinement of the thermal damage into the dermis. The different cooling temperatures did not provide detectable differences in terms of size and depth of thermal damage. New collagen synthesis was confirmed by a marked fibroblastic proliferation, detected in the lower dermis at D3 and clearly seen in the upper dermis at D7. This new laser appears to be a promising new tool for the treatment of skin laxity, solar elastosis, facial rhytids and mild reduction of wrinkles.

Differentiation of ventricular and supraventricular tachycardias based on the analysis of the first postpacing interval after sequential anti-tachycardia pacing in implantable cardioverter-defibrillator patients.

PubMed

Arenal, Angel; Ortiz, Mercedes; Peinado, Rafael; Merino, Jose L; Quesada, Aurelio; Atienza, Felipe; Alberola, Arcadio García; Ormaetxe, Jose; Castellanos, Eduardo; Rodriguez, Juan C; Pérez, Nicasio; García, Javier; Boluda, Luis; del Prado, Mario; Artés, Antonio

2007-03-01

Current discrimination algorithms do not completely avoid inappropriate tachycardia detection. This study analyzes the discrimination capability of the changes of the first postpacing interval (FPPI) after successive bursts of anti-tachycardia pacing (ATP) trains in implantable cardioverter-defibrillator (ICD)-recorded tachycardias. We included 50 ICD patients in this prospective study. We hypothesized that the FPPI variability (FPPIV) when comparing bursts with different numbers of beats would be shorter in ventricular tachycardias (VTs) compared with supraventricular tachycardias (SVTs). The ATP (5-10 pulses, 91% of tachycardia cycle length) was programmed for tachycardias >240 ms. Anti-tachycardia pacing was delivered during 37 sinus tachycardias (STs) in an exercise test, 96 induced VTs in an electrophysiological study, and 198 spontaneous episodes (144 VTs and 54 SVTs). The FPPI remained stable after all ATP bursts in VT but changed continuously in SVT; when comparing bursts of 5 and 10 pulses, the FPPIV was shorter in VT (34 +/- 65 vs.138 +/- 69, P<.0001, in all T and 12 +/- 20 vs. 138 +/- 69, P<.0001, in T>or=320 ms) than in SVT. In T>or=320 ms an FPPIV

Observation of nanosecond laser induced fluorescence of in vitro seawater phytoplankton

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bensky, Thomas J.; Clemo, Lisa; Gilbert, Chris

2008-08-01

Seawater has been irradiated using a train of 70 ns flashes from a 440 nm laser source. This wavelength is on resonance with the blue absorption peak of Chlorophyll pigment associated with the photosystem of in vitro phytoplankton. The resulting fluorescence at 685 nm is instantaneously recorded during each laser pulse using a streak camera. Delayed fluorescence is observed, yielding clues about initiation of the photosynthetic process on a nanosecond time scale. Further data processing allows for determination of the functional absorption cross section, found to be 0.0095 ?{sup 2}, which is the first reporting of this number for inmore » vitro phytoplankton. Unlike other flash-pump studies of Chlorophyll, using a LED or flashlamp-based sources, the short laser pulse used here does not reveal any pulse-to-pulse hysteresis (i.e., variable fluorescence), indicating that the laser pulses used here are not able to drive the photosynthetic process to completion. This is attributed to competition from a back reaction between the photoexcited photosystem II and the intermediate electron acceptor. The significance of this work as a new type of deployable ocean fluorimeter is discussed, and it is believed the apparatus will have applications in thin-layer phytoplankton research.« less

A real-time pulsed photon dosimeter

NASA Astrophysics Data System (ADS)

Brown, David; Olsher, Richard H.; Eisen, Yosef; Rodriguez, Joseph F.

1996-02-01

Radiation sources producing short pulses of photon radiation are now widespread. Such sources include electron and proton linear accelerators, betatrons, synchrotrons, and field-emission impulse generators. It is often desirable to measure leakage and skyshine radiation from such sources in real time, on a single-pulse basis as low as 8.7 nGy (1 μR) per pulse. This paper describes the design and performance of a prototype, real-time, pulsed photon dosimeter (PPD) capable of single-pulse dose measurements over the range from 3.5 nGy to 3.5 μGy (0.4 to 400 μR). The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of radiation pulses over a 3-s period. A pulse repetition rate of up to 300 Hz is accommodated. The design is eminently suitable for packaging as a lightweight, portable, survey meter. The PPD uses a CdWO 4 scintillator optically coupled to a photodiode to generate a charge at the diode output. A pulse amplifier converts the charge to a voltage pulse. A digitizer circuit generates a burst of logic pulses whose number is proportional to the peak value of the voltage pulse. The digitizer output is recorded by a pulse counter and suitably displayed. A prototype PPD was built for testing and evaluation purposes. The performance of the PPD was evaluated with a variety of pulsed photon sources. The dynamic range, energy response, and response to multiple pulses were characterized. The experimental data confirm the viability of the PPD for pulsed photon dosimetry.

Temperature dependent exchange bias training effect in single-crystalline BiFeO{sub 3}/Co bilayers

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, M. C.; You, B.; Tu, H. Q.

2015-05-07

Single-crystalline BiFeO{sub 3} (BFO)/Co bilayers were prepared by combined pulsed laser deposition and magnetron sputtering on (001) SrTiO{sub 3} substrates. Exchange bias (EB) and accompanying training effect have been studied as a function of temperature (T) between 5 K and 300 K. A non-monotonic exchange field variation with sharp increase below 100 K has been observed. In the meanwhile, strong training effect was recorded when T < 100 K and it weakens monotonically with increasing T up to 300 K. These temperature dependent EB and training effect may be caused by the uncompensated spins in both the interfacial spin-glass (SG) phase at low temperature and the antiferromagneticmore » BFO layer at higher temperature. The low temperature EB training results can be well fitted by a modified Binek's model considering asymmetric changes of the pinning SG spins at the descending and the ascending branches.« less

Linear induction accelerator

DOEpatents

Buttram, M.T.; Ginn, J.W.

1988-06-21

A linear induction accelerator includes a plurality of adder cavities arranged in a series and provided in a structure which is evacuated so that a vacuum inductance is provided between each adder cavity and the structure. An energy storage system for the adder cavities includes a pulsed current source and a respective plurality of bipolar converting networks connected thereto. The bipolar high-voltage, high-repetition-rate square pulse train sets and resets the cavities. 4 figs.

Microprocessor-based cardiotachometer

NASA Technical Reports Server (NTRS)

Crosier, W. G.; Donaldson, J. A.

1981-01-01

Instrument operates reliably even with stress-test electrocardiogram (ECG) signals subject to noise, baseline wandering, and amplitude change. It records heart rate from preamplified, single-lead ECG input signal and produces digital and analog heart-rate outputs which are fed elsewhere. Analog hardware processes ECG input signal, producing 10-ms pulse for each heartbeat. Microprocessor analyzes resulting pulse train, identifying irregular heartbeats and maintaining stable output during lead switching. Easily modified computer program provides analysis.

Pulse-rate discrimination by cochlear-implant and normal-hearing listeners with and without binaural cues

PubMed Central

Carlyon, Robert P.; Long, Christopher J.; Deeks, John M.

2008-01-01

Experiment 1 measured rate discrimination of electric pulse trains by bilateral cochlear implant (CI) users, for standard rates of 100, 200, and 300 pps. In the diotic condition the pulses were presented simultaneously to the two ears. Consistent with previous results with unilateral stimulation, performance deteriorated at higher standard rates. In the signal interval of each trial in the dichotic condition, the standard rate was presented to the left ear and the (higher) signal rate was presented to the right ear; the non-signal intervals were the same as in the diotic condition. Performance in the dichotic condition was better for some listeners than in the diotic condition for standard rates of 100 and 200 pps, but not at 300 pps. It is concluded that the deterioration in rate discrimination observed for CI users at high rates cannot be alleviated by the introduction of a binaural cue, and is unlikely to be limited solely by central pitch processes. Experiment 2 performed an analogous experiment in which 300-pps acoustic pulse trains were bandpass filtered (3900-5400 Hz) and presented in a noise background to normal-hearing listeners. Unlike the results of experiment 1, performance was superior in the dichotic than in the diotic condition. PMID:18397032

2.36 J, 50 Hz nanosecond pulses from a diode side-pumped Nd:YAG MOPA system

NASA Astrophysics Data System (ADS)

Li, Chaoyang; Lu, Chengqiang; Li, Chuan; Yang, Ning; Li, Ye; Yang, Zhen; Han, Song; Shi, Junfeng; Zhou, Zewu

2017-07-01

We report on a high-energy high-repetition-rate nanosecond Nd:YAG main oscillator power amplifier (MOPA) system. Maximum output pulse energy of 2.36 J with duration of 9.4 ns at 50 Hz has been achieved. The master oscillator was a LD side-pumped electro-optical Q-switched Nd:YAG rod laser adopting unstable cavity with variable reflectivity mirror (VRM). It delivered a pulse train with energy up to 180 mJ and pulse duration of 10.7 ns. The near-field pattern demonstrated a nearly super Gaussian flat top profile. In the amplification stage, the pulse was boosted via double-pass two Nd:YAG rod amplifiers. Maximum pulse energy was obtained at the peak pump power of 37.5 kW, corresponding to an optical-optical conversion efficiency of 25.2%. The correlative peak power was deduced to be 251 MW. We also presented the result of 100 Hz nanosecond laser with average output power of >100 W.

Resonant optical pulses on a continuous-wave background in two-level active media

NASA Astrophysics Data System (ADS)

Li, Sitai; Biondini, Gino; Kovačič, Gregor; Gabitov, Ildar

2018-01-01

We present exact N-soliton optical pulses riding on a continuous-wave (c.w.) beam that propagate through and interact with a two-level active optical medium. Their representation is derived via an appropriate generalization of the inverse scattering transform for the corresponding Maxwell-Bloch equations. We describe the single-soliton solutions in detail and classify them into several distinct families. In addition to the analogues of traveling-wave soliton pulses that arise in the absence of a c.w. beam, we obtain breather-like structures, periodic pulse-trains and rogue-wave-type (i.e., rational) pulses, whose existence is directly due to the presence of the c.w. beam. These soliton solutions are the analogues for Maxwell-Bloch systems of the four classical solution types of the focusing nonlinear Schrödinger equation with non-zero background, although the physical behavior of the corresponding solutions is quite different.

Long distance measurement with a femtosecond laser based frequency comb

NASA Astrophysics Data System (ADS)

Bhattacharya, N.; Cui, M.; Zeitouny, M. G.; Urbach, H. P.; van den Berg, S. A.

2017-11-01

Recent advances in the field of ultra-short pulse lasers have led to the development of reliable sources of carrier envelope phase stabilized femtosecond pulses. The pulse train generated by such a source has a frequency spectrum that consists of discrete, regularly spaced lines known as a frequency comb. In this case both the frequency repetition and the carrier-envelope-offset frequency are referenced to a frequency standard, like an atomic clock. As a result the accuracy of the frequency standard is transferred to the optical domain, with the frequency comb as transfer oscillator. These unique properties allow the frequency comb to be applied as a versatile tool, not only for time and frequency metrology, but also in fundamental physics, high-precision spectroscopy, and laser noise characterization. The pulse-to-pulse phase relationship of the light emitted by the frequency comb has opened up new directions for long range highly accurate distance measurement.

Theoretical exploration of control factors for the high-order harmonic generation (HHG) spectrum in two-color field.

PubMed

Huang, Xinting; Yang, Dapeng; Yao, Li

2014-09-15

In this work, the laser-parameter effects on the high-order harmonic generation (HHG) spectrum and attosecond trains by mixing two-color laser field, a visible light field of 800 nm and a mid-infrared (mid-IR) laser pulses of 2400 nm, are theoretically demonstrated for the first time. Different schemes are applied to discuss the function of intensity, carrier-envelope phase (CEP) and pulse duration on the generation of an isolated attosecond pulse. As a consequence, an isolated 16as pulse is obtained by Fourier transforming an ultrabroad XUV continuum of 208 eV with the fundamental field of duration of 6 fs, 9×10(14)W/cm2 of intensity, the duration of 12 fs, the CEPs of the two driving pulses of -π and the relative strength ratio √R=0.2. Copyright © 2014 Elsevier B.V. All rights reserved.

High peak power actively Q-switched mid-infrared fiber lasers at 3 μm

NASA Astrophysics Data System (ADS)

Shen, Yanlong; Wang, Yishan; Luan, Kunpeng; Chen, Hongwei; Tao, Mengmeng; Si, Jinhai

2017-04-01

Diode-pumped pulsed Er3+-doped ZBLAN fiber lasers at 2.8 μm actively Q-switched by using an mechanical Q-switch with feedbacks of a protected gold mirror and a blazing grating were investigated, respectively. A pulse energy of 0.13 mJ and repetition rate of 10 kHz with a pulse width of 127.3 ns at 2.78 μm was obtained when using a protected gold mirror as the feedback. By replacing the mirror with a blazing grating in Littrow configuration, the wavelength of the Q-switched pulse train was tunable with over 100 nm tuning range from 2.71 to 2.82 μm and a linewidth of 1.5 nm. A maxinmum pulse energy of up to 0.15 mJ and repetition rate of 10 kHz with a pulse width of 92.6 ns was achieved, yielding the maximum peak power of exceeding 1.6 kW. The pulse energy and peak power, to our knowledge, are the highest ever reported in the mid-infrared Q-switched fiber lasers.

Predicting non-isometric fatigue induced by electrical stimulation pulse trains as a function of pulse duration

PubMed Central

2013-01-01

Background Our previous model of the non-isometric muscle fatigue that occurs during repetitive functional electrical stimulation included models of force, motion, and fatigue and accounted for applied load but not stimulation pulse duration. Our objectives were to: 1) further develop, 2) validate, and 3) present outcome measures for a non-isometric fatigue model that can predict the effect of a range of pulse durations on muscle fatigue. Methods A computer-controlled stimulator sent electrical pulses to electrodes on the thighs of 25 able-bodied human subjects. Isometric and non-isometric non-fatiguing and fatiguing knee torques and/or angles were measured. Pulse duration (170–600 μs) was the independent variable. Measurements were divided into parameter identification and model validation subsets. Results The fatigue model was simplified by removing two of three non-isometric parameters. The third remained a function of other model parameters. Between 66% and 77% of the variability in the angle measurements was explained by the new model. Conclusion Muscle fatigue in response to different stimulation pulse durations can be predicted during non-isometric repetitive contractions. PMID:23374142

Pure antimony film as saturable absorber for Q-switched erbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Rahman, M. F. A.; Zhalilah, M. Z.; Latiff, A. A.; Rosol, A. H. A.; Lokman, M. Q.; Bushroa, A. R.; Dimyati, K.; Harun, S. W.

2018-04-01

This paper reports on the use of Antimony (Sb) polymer film to generate stable Q-switching pulses in Erbium-doped fiber laser (EDFL) cavity. The SA is fabricated by coating a thin layer of Sb on a polyvinyl alcohol (PVA) film through physical vapour deposition (PVD) process. A 1 × 1 mm area of the film SA is cut and integrated into between two fiber ferrules inside the laser cavity for intra-cavity loss modulation. Self-starting and stable Q-switched pulses are obtained within a pump power range from 60 to 142 mW. Within this range, the repetition rate increases from 70.82 to 98.04 kHz, while pulse width decreases from 7.42 to 5.36 μs. The fundamental frequency signal-to-noise ratio of the pulse signal is 74 dB, which indicates the excellent stability of the pulses. The maximum output power and pulse energy are 8.45 mW and 86.19 nJ, respectively. Our demonstration shows that Sb film SA capable of generating stable pulses train operating at 1.55-micron region.

Effects of interaural time differences in fine structure and envelope on lateral discrimination in electric hearing.

PubMed

Majdak, Piotr; Laback, Bernhard; Baumgartner, Wolf-Dieter

2006-10-01

Bilateral cochlear implant (CI) listeners currently use stimulation strategies which encode interaural time differences (ITD) in the temporal envelope but which do not transmit ITD in the fine structure, due to the constant phase in the electric pulse train. To determine the utility of encoding ITD in the fine structure, ITD-based lateralization was investigated with four CI listeners and four normal hearing (NH) subjects listening to a simulation of electric stimulation. Lateralization discrimination was tested at different pulse rates for various combinations of independently controlled fine structure ITD and envelope ITD. Results for electric hearing show that the fine structure ITD had the strongest impact on lateralization at lower pulse rates, with significant effects for pulse rates up to 800 pulses per second. At higher pulse rates, lateralization discrimination depended solely on the envelope ITD. The data suggest that bilateral CI listeners benefit from transmitting fine structure ITD at lower pulse rates. However, there were strong interindividual differences: the better performing CI listeners performed comparably to the NH listeners.

A comparison of models of the isometric force of locust skeletal muscle in response to pulse train inputs.

PubMed

Wilson, Emma; Rustighi, Emiliano; Newland, Philip L; Mace, Brian R

2012-03-01

Muscle models are an important tool in the development of new rehabilitation and diagnostic techniques. Many models have been proposed in the past, but little work has been done on comparing the performance of models. In this paper, seven models that describe the isometric force response to pulse train inputs are investigated. Five of the models are from the literature while two new models are also presented. Models are compared in terms of their ability to fit to isometric force data, using Akaike's and Bayesian information criteria and by examining the ability of each model to describe the underlying behaviour in response to individual pulses. Experimental data were collected by stimulating the locust extensor tibia muscle and measuring the force generated at the tibia. Parameters in each model were estimated by minimising the error between the modelled and actual force response for a set of training data. A separate set of test data, which included physiological kick-type data, was used to assess the models. It was found that a linear model performed the worst whereas a new model was found to perform the best. The parameter sensitivity of this new model was investigated using a one-at-a-time approach, and it found that the force response is not particularly sensitive to changes in any parameter.

Superior Effects of High-Intensity Interval Training vs. Moderate Continuous Training on Arterial Stiffness in Episodic Migraine: A Randomized Controlled Trial.

PubMed

Hanssen, Henner; Minghetti, Alice; Magon, Stefano; Rossmeissl, Anja; Papadopoulou, Athina; Klenk, Christopher; Schmidt-Trucksäss, Arno; Faude, Oliver; Zahner, Lukas; Sprenger, Till; Donath, Lars

2017-01-01

Background: Migraine is associated with increased cardiovascular risk and vascular dysfunction. Since aerobic exercise can reduce cardiovascular risk, the present randomized controlled trail aimed at investigating the effects of high-intensity interval training (HIT) vs. moderate continuous exercise training (MCT) on arterial stiffness in migraine patients. Methods: Forty-eight episodic migraineurs were initially enrolled in the study. 37 patients [female: 30; age: 37 ( SD : 10); BMI: 23.1 (5.2); Migraine days per month: 3.7 (2.5)] completed the intervention. Central blood pressure, pulse wave reflection, and aortic pulse wave velocity (PWV) were obtained by an oscillometric monitor. Incremental treadmill exercise testing yielded maximal and submaximal fitness parameters. Participants were randomly assigned to either HIT, MCT, or a control group (CON). The intervention groups trained twice a week over a 12-week intervention period. Results: After adjustment for between-group baseline differences, a moderate meaningful overall reduction of the augmentation index at 75 min -1 heart rate (AIx@75) was observed [partial eta squared ([Formula: see text]) = 0.16; p = 0.06]. With 91% likely beneficial effects, HIT was more effective in reducing AIx@75 than MCT [HIT: pre 22.0 (9.7), post 14.9 (13.0), standardized mean difference (SMD) = 0.62; MCT: pre 16.6 (8.5), post 21.3 (10.4), SMD -0.49]. HIT induced a relevant reduction in central systolic blood pressure [cSBP: pre 118 (23) mmHg, post 110 (16) mmHg, SMD = 0.42] with a 59% possibly beneficial effect compared to CON, while MCT showed larger effects in lowering central diastolic blood pressure [pre 78 (7) mmHg, post 74 (7) mmHg, SMD = 0.61], presenting 60% possibly beneficial effects compared to CON. Central aortic PWV showed no changes in any of the three groups. Migraine days were reduced more successfully by HIT than MCT (HIT: SMD = 1.05; MCT: SMD = 0.43). Conclusion: HIT but not MCT reduces AIx@75 as a measure of pulse wave reflection and indirect marker of systemic arterial stiffness. Both exercise modalities beneficially affect central blood pressure. HIT proved to be an effective complementary treatment option to reduce vascular dysfunction and blood pressure in migraineurs.

Assessment of the generalization of learned image reconstruction and the potential for transfer learning.

PubMed

Knoll, Florian; Hammernik, Kerstin; Kobler, Erich; Pock, Thomas; Recht, Michael P; Sodickson, Daniel K

2018-05-17

Although deep learning has shown great promise for MR image reconstruction, an open question regarding the success of this approach is the robustness in the case of deviations between training and test data. The goal of this study is to assess the influence of image contrast, SNR, and image content on the generalization of learned image reconstruction, and to demonstrate the potential for transfer learning. Reconstructions were trained from undersampled data using data sets with varying SNR, sampling pattern, image contrast, and synthetic data generated from a public image database. The performance of the trained reconstructions was evaluated on 10 in vivo patient knee MRI acquisitions from 2 different pulse sequences that were not used during training. Transfer learning was evaluated by fine-tuning baseline trainings from synthetic data with a small subset of in vivo MR training data. Deviations in SNR between training and testing led to substantial decreases in reconstruction image quality, whereas image contrast was less relevant. Trainings from heterogeneous training data generalized well toward the test data with a range of acquisition parameters. Trainings from synthetic, non-MR image data showed residual aliasing artifacts, which could be removed by transfer learning-inspired fine-tuning. This study presents insights into the generalization ability of learned image reconstruction with respect to deviations in the acquisition settings between training and testing. It also provides an outlook for the potential of transfer learning to fine-tune trainings to a particular target application using only a small number of training cases. © 2018 International Society for Magnetic Resonance in Medicine.

Ultrafast mode-locked fiber lasers for high-speed OTDM transmission and related topics

NASA Astrophysics Data System (ADS)

Nakazawa, Masataka

Ultrashort optical pulse sources in the 1.5-µm region are becoming increasingly important in terms of realizing ultrahigh-speed optical transmission and signal processing at optical nodes. This paper provides a detailed description of several types of mode-locked erbium-doped fiber laser, which are capable of generating picosecond-femtosecond optical pulses in the 1.55-µm region. In terms of ultrashort pulse generation at a low repetition rate (˜100 MHz), passively mode-locked fiber lasers enable us to produce pulses of approximately 100 fs. With regard to high repetition rate pulse generation at 10-40 GHz, harmonically mode-locked fiber lasers can produce picosecond pulses. This paper also describes the generation of a femtosecond pulse train at a repetition rate of 10-40 GHz by compressing the output pulses from harmonically mode-locked fiber lasers with dispersion-decreasing fibers. Finally, a new Cs optical atomic clock at a frequency of 9.1926 GHz is reported that uses a re-generatively mode-locked fiber laser as an opto-electronic oscillator instead of a quartz oscillator. The repetition rate stability reaches as high as 10-12-10-13.

First pulse effect self-suppression picosecond regenerative amplifier (Conference Presentation)

NASA Astrophysics Data System (ADS)

Fan, Haitao; Chang, Liang; Zhang, Yi; Yao, Siyi; Lu, Wei; Yang, Xiaohong

2017-03-01

First pulse effect, commonly seen in nanosecond cavity-dumped lasers and picosecond regenerative amplifiers, not only leads to degradation of processing quality, but also acts as potential threat to optical switching elements. Several methods have been developed to suppress that effect, including electronic controls, polarization controls, and diffraction controls. We present a new way for first pulse self-suppression without any additional components. By carefully arranging the cavity mirror of a regenerative amplifier, we realized `parasitic lasing like' radiation. When the regenerative amplifier works in `operation ready' status, the parasitic lasing occurs and prevents the gain crystal from saturation. When the regenerative amplifier starts working and amplifying pulses, the first pulse in a pulse train will not get much more gain and energy than pulses following it. As parasitic lasing disappears at the same time, the average output power of the amplifier does not significantly reduce. This cost effective method does not require any additional component. In addition, as it is not polarization dependent, this method is widely suitable for different kinds of regenerative amplifiers. It's the easiest and cheapest way to suppress first pulse effect, to the best of our knowledge.

Modulatory effects of high-frequency repetitive transcranial magnetic stimulation on the ipsilateral silent period.

PubMed

Cincotta, M; Giovannelli, F; Borgheresi, A; Balestrieri, F; Zaccara, G; Inghilleri, M; Berardelli, A

2006-06-01

In healthy subjects, suprathreshold repetitive transcranial magnetic stimulation (rTMS) at frequencies >2 Hz prolongs the cortical silent period (CSP) over the course of the train. This progressive lengthening probably reflects temporal summation of the inhibitory interneurons in the stimulated primary motor cortex (M1). In this study, we tested whether high-frequency rTMS also modulates the ipsilateral silent period (ISP). In nine normal subjects, suprathreshold 10-pulse rTMS trains were delivered to the right M1 at frequencies of 3, 5, and 10 Hz during maximal isometric contraction of both first dorsal interosseous muscles. At 10 Hz, the second pulse of the train increased the area of the ISP; the other stimuli did not increase it further. During rTMS at 3 and 5 Hz, the ISP remained significantly unchanged. Control experiments showed that 10-Hz rTMS delivered at subthreshold intensity also increased the ISP. rTMS over the hand motor area did not facilitate ISPs in the biceps muscles. Finally, rTMS-induced ISP facilitation did not outlast the 10-Hz rTMS train. These findings suggest that rTMS at a frequency of 10 Hz potentiates the interhemispheric inhibitory mechanisms responsible for the ISP, partly through temporal summation. The distinct changes in the ISP and CSP suggest that rTMS facilitates intrahemispheric and interhemispheric inhibitory phenomena through separate neural mechanisms. The ISP facilitation induced by high-frequency rTMS is a novel, promising tool to investigate pathophysiological abnormal interhemispheric inhibitory transfer in various neurological diseases.

Adaptive changes in the neuromagnetic response of the primary and association somatosensory areas following repetitive tactile hand stimulation in humans

PubMed Central

Popescu, Anda; Barlow, Steven; Venkatesan, Lalit; Wang, Jingyan; Popescu, Mihai

2014-01-01

Cortical adaptation in the primary somatosensory cortex (SI) has been probed using different stimulation modalities and recording techniques, in both human and animal studies. In contrast, considerably less knowledge has been gained about the adaptation profiles in other areas of the cortical somatosensory network. Using magnetoencephalography, we examined the patterns of short-term adaptation for evoked responses in SI and somatosensory association areas during tactile stimulation applied to the glabrous skin of the right hand. Cutaneous stimuli were delivered as trains of serial pulses with a constant frequency of 2 Hz and 4 Hz in separate runs, and a constant inter-train interval of 5 s. The unilateral stimuli elicited transient responses to the serial pulses in the train, with several response components that were separated by Independent Component Analysis. Subsequent neuromagnetic source reconstruction identified regional generators in the contralateral SI and somatosensory association areas in the posterior parietal cortex (PPC). Activity in the bilateral secondary somatosensory cortex (i.e. SII/PV) was also identified, although less consistently across subjects. The dynamics of the evoked activity in each area and the frequency-dependent adaptation effects were assessed from the changes in the relative amplitude of serial responses in each train. We show that the adaptation profiles in SI and PPC can be quantitatively characterized from neuromagnetic recordings using tactile stimulation, with the sensitivity to repetitive stimulation increasing from SI to PPC. A similar approach for SII/PV has proven less straightforward, potentially due to the selective nature of these areas to respond predominantly to certain stimuli. PMID:22331631

Round-robin differential-phase-shift quantum key distribution with heralded pair-coherent sources

NASA Astrophysics Data System (ADS)

Wang, Le; Zhao, Shengmei

2017-04-01

Round-robin differential-phase-shift (RRDPS) quantum key distribution (QKD) scheme provides an effective way to overcome the signal disturbance from the transmission process. However, most RRDPS-QKD schemes use weak coherent pulses (WCPs) as the replacement of the perfect single-photon source. Considering the heralded pair-coherent source (HPCS) can efficiently remove the shortcomings of WCPs, we propose a RRDPS-QKD scheme with HPCS in this paper. Both infinite-intensity decoy-state method and practical three-intensity decoy-state method are adopted to discuss the tight bound of the key rate of the proposed scheme. The results show that HPCS is a better candidate for the replacement of the perfect single-photon source, and both the key rate and the transmission distance are greatly increased in comparison with those results with WCPs when the length of the pulse trains is small. Simultaneously, the performance of the proposed scheme using three-intensity decoy states is close to that result using infinite-intensity decoy states when the length of pulse trains is small.

Dynamic characteristics of corona discharge generated under rainfall condition on AC charged conductors

NASA Astrophysics Data System (ADS)

Xu, Pengfei; Zhang, Bo; Wang, Zezhong; Chen, Shuiming; He, Jinliang

2017-12-01

By synchronous measurement of corona current and the water droplet deformation process on a conductor surface, different types of corona discharge are visualized when AC voltage is applied on a line-ground electrode system. The corona characteristics are closely related to the applied voltage and water supply rate. With the increase of AC voltage, the positive Taylor cone discharge firstly appears and then disappears, replaced by the dripping and crashing discharge. Furthermore, the number of pulses in each pulse train increases with the increase of applied voltage. The mechanism of the transfer from the positive Taylor cone discharge to the dripping and crashing discharge is found to be related to the oscillation process of the water droplet. The water supply rate also has a great influence on the characteristics of corona currents. The number of positive pulse trains increases linearly when the water supply rate gets larger, leading to a higher audible noise and radio interference level from the AC corona, which is quite different from that of the DC corona. The difference between the AC and DC coronas under rainfall conditions is analyzed finally.

Ultrafast entanglement of trapped ions

NASA Astrophysics Data System (ADS)

Neyenhuis, Brian; Mizrahi, Jonathan; Johnson, Kale; Monroe, Christopher

2013-05-01

We have demonstrated ultrafast spin-motion entanglement of a single atomic ion using a short train of intense laser pulses. This pulse train gives the ion a spin-dependent kick where each spin state receives a discrete momentum kick in opposite directions. Using a series of these spin-dependent kicks we can realize a two qubit gate. In contrast to gates using spectroscopically resolved motional sidebands, these gates may be performed faster than the trap oscillation period, making them potentially less sensitive to noise, independent of temperature, and more easily scalable to large crystals of ions. We show that multiple kicks can be strung together to create a ``Schrodinger cat'' like state, where the large separation between the two parts of the wavepacket allow us to accumulate the phase shift necessary for a gate in a shorter amount of time. We will present a realistic pulse scheme for a two ion gate, and our progress towards its realization. This work is supported by grants from the U.S. Army Research Office with funding from the DARPA OLE program, IARPA, and the MURI program; and the NSF Physics Frontier Center at JQI.

Boxcar detection for high-frequency modulation in stimulated Raman scattering microscopy

NASA Astrophysics Data System (ADS)

Fimpel, P.; Riek, C.; Ebner, L.; Leitenstorfer, A.; Brida, D.; Zumbusch, A.

2018-04-01

Stimulated Raman scattering (SRS) microscopy is an important non-linear optical technique for the investigation of unlabeled samples. The SRS signal manifests itself as a small intensity exchange between the laser pulses involved in coherent excitation of Raman modes. Usually, high-frequency modulation is applied in one pulse train, and the signal is then detected on the other pulse train via lock-in amplification. While allowing shot-noise limited detection sensitivity, lock-in detection, which corresponds to filtering the signal in the frequency domain, is not the most efficient way of using the excitation light. In this manuscript, we show that boxcar averaging, which is equivalent to temporal filtering, is better suited for the detection of low-duty-cycle signals as encountered in SRS microscopy. We demonstrate that by employing suitable gating windows, the signal-to-noise ratios achievable with lock-in detection can be realized in shorter time with boxcar averaging. Therefore, high-quality images are recorded at a faster rate and lower irradiance which is an important factor, e.g., for minimizing degradation of biological samples.

Interpolator for numerically controlled machine tools

DOEpatents

Bowers, Gary L.; Davenport, Clyde M.; Stephens, Albert E.

1976-01-01

A digital differential analyzer circuit is provided that depending on the embodiment chosen can carry out linear, parabolic, circular or cubic interpolation. In the embodiment for parabolic interpolations, the circuit provides pulse trains for the X and Y slide motors of a two-axis machine to effect tool motion along a parabolic path. The pulse trains are generated by the circuit in such a way that parabolic tool motion is obtained from information contained in only one block of binary input data. A part contour may be approximated by one or more parabolic arcs. Acceleration and initial velocity values from a data block are set in fixed bit size registers for each axis separately but simultaneously and the values are integrated to obtain the movement along the respective axis as a function of time. Integration is performed by continual addition at a specified rate of an integrand value stored in one register to the remainder temporarily stored in another identical size register. Overflows from the addition process are indicative of the integral. The overflow output pulses from the second integration may be applied to motors which position the respective machine slides according to a parabolic motion in time to produce a parabolic machine tool motion in space. An additional register for each axis is provided in the circuit to allow "floating" of the radix points of the integrand registers and the velocity increment to improve position accuracy and to reduce errors encountered when the acceleration integrand magnitudes are small when compared to the velocity integrands. A divider circuit is provided in the output of the circuit to smooth the output pulse spacing and prevent motor stall, because the overflow pulses produced in the binary addition process are spaced unevenly in time. The divider has the effect of passing only every nth motor drive pulse, with n being specifiable. The circuit inputs (integrands, rates, etc.) are scaled to give exactly n times the desired number of pulses out, in order to compensate for the divider.

Circadian system of mice integrates brief light stimuli.

PubMed

Van Den Pol, A N; Cao, V; Heller, H C

1998-08-01

Light is the primary sensory stimulus that synchronizes or entrains the internal circadian rhythms of animals to the solar day. In mammals photic entrainment of the circadian pacemaker residing in the suprachiasmatic nuclei is due to the fact that light at certain times of day can phase shift the pacemaker. In this study we show that the circadian system of mice can integrate extremely brief, repeated photic stimuli to produce large phase shifts. A train of 2-ms light pulses delivered as one pulse every 5 or 60 s, with a total light duration of 120 ms, can cause phase shifts of several hours that endure for weeks. Single 2-ms pulses of light were ineffective. Thus these data reveal a property of the mammalian circadian clock: it can integrate and store latent sensory information in such a way that a series of extremely brief photic stimuli, each too small to cause a phase shift individually, together can cause a large and long-lasting change in behavior.

Helicity-Selective Phase-Matching and Quasi-Phase matching of Circularly Polarized High-Order Harmonics: Towards Chiral Attosecond Pulses

DTIC Science & Technology

2016-05-23

Invited Article Helicity-selective phase-matching and quasi -phase matching of circularly polarized high-order harmonics: towards chiral attosecond...chromatic lasers was recently predicted theoretically and demonstrated experimentally . In that work, phase matching was analyzed by assuming that the...Indeed, we present an experimentally measured chiral spectrum that can support a train of attosecond pulses with a high degree of circular polarization

The Electrically Evoked Auditory Change Complex Evoked by Temporal Gaps Using Cochlear Implants or Auditory Brainstem Implants in Children With Cochlear Nerve Deficiency.

PubMed

He, Shuman; McFayden, Tyler C; Shahsavarani, Bahar S; Teagle, Holly F B; Ewend, Matthew; Henderson, Lillian; Buchman, Craig A

This study aimed to (1) establish the feasibility of measuring the electrically evoked auditory change complex (eACC) in response to temporal gaps in children with cochlear nerve deficiency (CND) who are using cochlear implants (CIs) and/or auditory brainstem implants (ABIs); and (2) explore the association between neural encoding of, and perceptual sensitivity to, temporal gaps in these patients. Study participants included 5 children (S1 to S5) ranging in age from 3.8 to 8.2 years (mean: 6.3 years) at the time of testing. All subjects were unilaterally implanted with a Nucleus 24M ABI due to CND. For each subject, two or more stimulating electrodes of the ABI were tested. S2, S3, and S5 previously received a CI in the contralateral ear. For these 3 subjects, at least two stimulating electrodes of their CIs were also tested. For electrophysiological measures, the stimulus was an 800-msec biphasic pulse train delivered to individual electrodes at the maximum comfortable level (C level). The electrically evoked responses, including the onset response and the eACC, were measured for two stimulation conditions. In the standard condition, the 800-msec pulse train was delivered uninterrupted to individual stimulating electrodes. In the gapped condition, a temporal gap was inserted into the pulse train after 400 msec of stimulation. Gap durations tested in this study ranged from 2 up to 128 msec. The shortest gap that could reliably evoke the eACC was defined as the objective gap detection threshold (GDT). For behavioral GDT measures, the stimulus was a 500-msec biphasic pulse train presented at the C level. The behavioral GDT was measured for individual stimulating electrodes using a one-interval, two-alternative forced-choice procedure. The eACCs to temporal gaps were recorded successfully in all subjects for at least one stimulating electrode using either the ABI or the CI. Objective GDTs showed intersubject variations, as well as variations across stimulating electrodes of the ABI or the CI within each subject. Behavioral GDTs were measured for one ABI electrode in S2 and for multiple ABI and CI electrodes in S5. All other subjects could not complete the task. S5 showed smaller behavioral GDTs for CI electrodes than those measured for ABI electrodes. One CI and two ABI electrodes in S5 showed comparable objective and behavioral GDTs. In contrast, one CI and two ABI electrodes in S5 and one ABI electrode in S2 showed measurable behavioral GDTs but no identifiable eACCs. The eACCs to temporal gaps were recorded in children with CND using either ABIs or CIs. Both objective and behavioral GDTs showed inter- and intrasubject variations. Consistency between results of eACC recordings and psychophysical measures of GDT was observed for some but not all ABI or CI electrodes in these subjects.

0.4 mJ quasi-continuously pumped picosecond Nd:GdVO4 laser with selectable pulse duration

NASA Astrophysics Data System (ADS)

Kubeček, V.; Jelínek, M.; Čech, M.; Hiršl, P.; Diels, J.-C.

2010-02-01

A quasi-continuously pumped picosecond oscillator-amplifier Nd:GdVO4 laser system based on two identical slabs in a single bounce geometry is reported. Pulse duration is from 160 to 55 ps resulting from the pulse shortening along the extended mode locked train from passively mode locked oscillator, which was measured directly from a single laser shot. The shortest 55 ps long cavity dumped single pulses from the oscillator with the energy of 15±1 μJ and the contrast better than 10-3 were amplified to the energy of 150 μJ with the contrast better than 10-3 after the single-pass amplification and to the energy of 400 μJ after the double-pass amplification.

The effect of scopolamine on matching behavior and the estimation of relative reward magnitude.

PubMed

Leon, Matthew I; Rodriguez-Barrera, Vanessa; Amaya, Aldo

2017-10-01

We investigated the behavioral effects of scopolamine on rats that bar pressed for trains of electrically stimulating pulses under concurrent variable interval schedules of reward. For the first half of the session (30 min) a 1:4 ratio in the programmed number of stimulation trains delivered at each option was in effect. At the start of the second half of the session, an unsignaled reversal in the relative train number (4:1) occurred. We tracked the relative magnitude of reward estimated for each contiguous pair of reinforced visits to competing options. Scopolamine hydrobromide led to a reduction in the relative magnitude of reward. A similar result was obtained in a follow-up test in which relative magnitude was manipulated by varying the pulse frequency of stimulation, while equating the train number at each option. The effect of scopolamine hydrobromide could not be attributed to undermatching, side bias, nor to an effect of scopolamine on the reward integration process. When the same rats were treated with scopolamine methylbromide, no effects on matching behavior were observed. Our results suggest a cholinergic basis for the computation of choice variables related to matching behavior. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Precise control of molecular dynamics with a femtosecond frequency comb.

PubMed

Pe'er, Avi; Shapiro, Evgeny A; Stowe, Matthew C; Shapiro, Moshe; Ye, Jun

2007-03-16

We present a general and highly efficient scheme for performing narrow-band Raman transitions between molecular vibrational levels using a coherent train of weak pump-dump pairs of shaped ultrashort pulses. The use of weak pulses permits an analytic description within the framework of coherent control in the perturbative regime, while coherent accumulation of many pulse pairs enables near unity transfer efficiency with a high spectral selectivity, thus forming a powerful combination of pump-dump control schemes and the precision of the frequency comb. Simulations verify the feasibility and robustness of this concept, with the aim to form deeply bound, ultracold molecules.

Time-domain measurement of optical transport in silicon micro-ring resonators.

PubMed

Pernice, Wolfram H P; Li, Mo; Tang, Hong X

2010-08-16

We perform time-domain measurements of optical transport dynamics in silicon nano-photonic devices. Using pulsed optical excitation the thermal and carrier induced optical nonlinearities of micro-ring resonators are investigated, allowing for identification of their individual contributions. Under pulsed excitation build-up of free carriers and heat in the waveguides leads to a beating oscillation of the cavity resonance frequency. When employing a burst of pulse trains shorter than the carrier life-time, the slower heating effect can be separated from the faster carrier effect. Our scheme provides a convenient way to thermally stabilize optical resonators for high-power time-domain applications and nonlinear optical conversion.

Broadband 2D electronic spectrometer using white light and pulse shaping: noise and signal evaluation at 1 and 100 kHz.

PubMed

Kearns, Nicholas M; Mehlenbacher, Randy D; Jones, Andrew C; Zanni, Martin T

2017-04-03

We have developed a broad bandwidth two-dimensional electronic spectrometer that operates shot-to-shot at repetition rates up to 100 kHz using an acousto-optic pulse shaper. It is called a two-dimensional white-light (2D-WL) spectrometer because the input is white-light supercontinuum. Methods for 100 kHz data collection are studied to understand how laser noise is incorporated into 2D spectra during measurement. At 100 kHz, shot-to-shot scanning of the delays and phases of the pulses in the pulse sequence produces a 2D spectrum 13-times faster and with the same signal-to-noise as using mechanical stages and a chopper. Comparing 100 to 1 kHz repetition rates, data acquisition time is decreased by a factor of 200, which is beyond the improvement expected by the repetition rates alone due to reduction in 1/f noise. These improvements arise because shot-to-shot readout and modulation of the pulse train at 100 kHz enables the electronic coherences to be measured faster than the decay in correlation between laser intensities. Using white light supercontinuum for the pump and probe pulses produces high signal-to-noise spectra on samples with optical densities <0.1 within a few minutes of averaging and an instrument response time of <46 fs thereby demonstrating that that simple broadband continuum sources, although weak, are sufficient to create high quality 2D spectra with >200 nm bandwidth.

Relationship Between Peripheral and Psychophysical Measures of Amplitude Modulation Detection in Cochlear Implant Users.

PubMed

Tejani, Viral D; Abbas, Paul J; Brown, Carolyn J

This study investigates the relationship between electrophysiological and psychophysical measures of amplitude modulation (AM) detection. Prior studies have reported both measures of AM detection recorded separately from cochlear implant (CI) users and acutely deafened animals, but no study has made both measures in the same CI users. Animal studies suggest a progressive loss of high-frequency encoding as one ascends the auditory pathway from the auditory nerve to the cortex. Because the CI speech processor uses the envelope of an ongoing acoustic signal to modulate pulse trains that are subsequently delivered to the intracochlear electrodes, it is of interest to explore auditory nerve responses to modulated stimuli. In addition, psychophysical AM detection abilities have been correlated with speech perception outcomes. Thus, the goal was to explore how the auditory nerve responds to AM stimuli and to relate those physiologic measures to perception. Eight patients using Cochlear Ltd. Implants participated in this study. Electrically evoked compound action potentials (ECAPs) were recorded using a 4000 pps pulse train that was sinusoidally amplitude modulated at 125, 250, 500, and 1000 Hz rates. Responses were measured for each pulse over at least one modulation cycle for an apical, medial, and basal electrode. Psychophysical modulation detection thresholds (MDTs) were also measured via a three-alternative forced choice, two-down, one-up adaptive procedure using the same modulation frequencies and electrodes. ECAPs were recorded from individual pulses in the AM pulse train. ECAP amplitudes varied sinusoidally, reflecting the sinusoidal variation in the stimulus. A modulated response amplitude (MRA) metric was calculated as the difference in the maximal and minimum ECAP amplitudes over the modulation cycles. MRA increased as modulation frequency increased, with no apparent cutoff (up to 1000 Hz). In contrast, MDTs increased as the modulation frequency increased. This trend is inconsistent with the physiologic measures. For a fixed modulation frequency, correlations were observed between MDTs and MRAs; this trend was evident at all frequencies except 1000 Hz (although only statistically significant for 250 and 500 Hz AM rates), possibly an indication of central limitations in processing of high modulation frequencies. Finally, peripheral responses were larger and psychophysical thresholds were lower in the apical electrodes relative to basal and medial electrodes, which may reflect better cochlear health and neural survival evidenced by lower preoperative low-frequency audiometric thresholds and steeper growth of neural responses in ECAP amplitude growth functions for apical electrodes. Robust ECAPs were recorded for all modulation frequencies tested. ECAP amplitudes varied sinusoidally, reflecting the periodicity of the modulated stimuli. MRAs increased as the modulation frequency increased, a trend we attribute to neural adaptation. For low modulation frequencies, there are multiple current steps between the peak and valley of the modulation cycle, which means successive stimuli are more similar to one another and neural responses are more likely to adapt. Higher MRAs were correlated with lower psychophysical thresholds at low modulation frequencies but not at 1000 Hz, implying a central limitation to processing of modulated stimuli.

Influence of cross-phase modulation in SPM-based nonlinear optical loop mirror

NASA Astrophysics Data System (ADS)

Pitois, Stéphane

2005-09-01

We study the role of cross-phase modulation (CPM) occurring between the two counter-propagating parts of a signal wave in a standard SPM-based nonlinear optical fiber loop mirror (NOLM). For pulse train with high duty-cycle, we experimentally observe the influence of cross-phase modulation on NOLM transmittivity. Finally, we propose a solution based on properly designed dispersion imbalanced NOLM to overcome undesirable CPM effects.

Involvement of IP3 Receptors in LTP and LTD Induction in Guinea Pig Hippocampal CA1 Neurons

ERIC Educational Resources Information Center

Taufiq, Ahmed Mostafa; Fujii, Satoshi; Yamazaki, Yoshihiko; Sasaki, Hiroshi; Kaneko, Kenya; Li, Jianmin; Kato, Hiroshi; Mikoshiba, Katsuhiko

2005-01-01

The role of inositol 1, 4, 5-trisphosphate receptors (IP3Rs) in long-term potentiation (LTP) and long-term depression (LTD) was studied in CA1 neurons in guinea pig hippocampal slices. In standard solution, short tetanic stimulation consisting of 15 pulses at 100 Hz induced LTP, while three short trains of low-frequency stimulation (LFS; 200…

Does short-term whole-body vibration training affect arterial stiffness in chronic stroke? A preliminary study

PubMed Central

Yule, Christie E.; Stoner, Lee; Hodges, Lynette D.; Cochrane, Darryl J.

2016-01-01

[Purpose] Previous studies have shown that stroke is associated with increased arterial stiffness that can be diminished by a program of physical activity. A novel exercise intervention, whole-body vibration (WBV), is reported to significantly improve arterial stiffness in healthy men and older sedentary adults. However, little is known about its efficacy in reducing arterial stiffness in chronic stroke. [Subjects and Methods] Six participants with chronic stroke were randomly assigned to 4 weeks of WBV training or control followed by cross-over after a 2-week washout period. WBV intervention consisted of 3 sessions of 5 min intermittent WBV per week for 4 weeks. Arterial stiffness (carotid arterial stiffness, pulse wave velocity [PWV], pulse and wave analysis [PWA]) were measured before/after each intervention. [Results] No significant improvements were reported with respect to carotid arterial stiffness, PWV, and PWA between WBV and control. However, carotid arterial stiffness showed a decrease over time following WBV compared to control, but this was not significant. [Conclusion] Three days/week for 4 weeks of WBV seems too short to elicit appropriate changes in arterial stiffness in chronic stroke. However, no adverse effects were reported, indicating that WBV is a safe and acceptable exercise modality for people with chronic stroke. PMID:27134400

Intermanual transfer and bilateral cortical plasticity is maintained in older adults after skilled motor training with simple and complex tasks

PubMed Central

Dickins, Daina S. E.; Sale, Martin V.; Kamke, Marc R.

2015-01-01

Intermanual transfer refers to the phenomenon whereby unilateral motor training induces performance gains in both the trained limb and in the opposite, untrained limb. Evidence indicates that intermanual transfer is attenuated in older adults following training on a simple ballistic movement task, but not after training on a complex task. This study investigated whether differences in plasticity in bilateral motor cortices underlie these differential intermanual transfer effects in older adults. Twenty young (<35 years-old) and older adults (>65 years) trained on a simple (repeated ballistic thumb abduction) and complex (sequential finger-thumb opposition) task in separate sessions. Behavioral performance was used to quantify intermanual transfer between the dominant (trained) and non-dominant (untrained) hands. The amplitude of motor-evoked potentials induced by single pulse transcranial magnetic stimulation was used to investigate excitability changes in bilateral motor cortices. Contrary to predictions, both age groups exhibited performance improvements in both hands after unilateral skilled motor training with simple and complex tasks. These performance gains were accompanied by bilateral increases in cortical excitability in both groups for the simple but not the complex task. The findings suggest that advancing age does not necessarily influence the capacity for intermanual transfer after training with the dominant hand. PMID:25999856

Combined effect of pulse density and grid cell size on predicting and mapping aboveground carbon in fast-growing Eucalyptus forest plantation using airborne LiDAR data.

PubMed

Silva, Carlos Alberto; Hudak, Andrew Thomas; Klauberg, Carine; Vierling, Lee Alexandre; Gonzalez-Benecke, Carlos; de Padua Chaves Carvalho, Samuel; Rodriguez, Luiz Carlos Estraviz; Cardil, Adrián

2017-12-01

LiDAR remote sensing is a rapidly evolving technology for quantifying a variety of forest attributes, including aboveground carbon (AGC). Pulse density influences the acquisition cost of LiDAR, and grid cell size influences AGC prediction using plot-based methods; however, little work has evaluated the effects of LiDAR pulse density and cell size for predicting and mapping AGC in fast-growing Eucalyptus forest plantations. The aim of this study was to evaluate the effect of LiDAR pulse density and grid cell size on AGC prediction accuracy at plot and stand-levels using airborne LiDAR and field data. We used the Random Forest (RF) machine learning algorithm to model AGC using LiDAR-derived metrics from LiDAR collections of 5 and 10 pulses m -2 (RF5 and RF10) and grid cell sizes of 5, 10, 15 and 20 m. The results show that LiDAR pulse density of 5 pulses m -2 provides metrics with similar prediction accuracy for AGC as when using a dataset with 10 pulses m -2 in these fast-growing plantations. Relative root mean square errors (RMSEs) for the RF5 and RF10 were 6.14 and 6.01%, respectively. Equivalence tests showed that the predicted AGC from the training and validation models were equivalent to the observed AGC measurements. The grid cell sizes for mapping ranging from 5 to 20 also did not significantly affect the prediction accuracy of AGC at stand level in this system. LiDAR measurements can be used to predict and map AGC across variable-age Eucalyptus plantations with adequate levels of precision and accuracy using 5 pulses m -2 and a grid cell size of 5 m. The promising results for AGC modeling in this study will allow for greater confidence in comparing AGC estimates with varying LiDAR sampling densities for Eucalyptus plantations and assist in decision making towards more cost effective and efficient forest inventory.

Vascular characteristics in young women-Effect of extensive endurance training or a sedentary lifestyle.

PubMed

Bjarnegård, N; Länne, T; Cinthio, M; Ekstrand, J; Hedman, K; Nylander, E; Henriksson, J

2018-06-01

To explore whether high-level endurance training in early age has an influence on the arterial wall properties in young women. Forty-seven athletes (ATH) and 52 controls (CTR), all 17-25 years of age, were further divided into runners (RUN), whole-body endurance athletes (WBA), sedentary controls (SC) and normally active controls (AC). Two-dimensional ultrasound scanning of the carotid arteries was conducted to determine local common carotid artery (CCA) geometry and wall distensibility. Pulse waves were recorded with a tonometer to determine regional pulse wave velocity (PWV) and pulse pressure waveform. Carotid-radial PWV was lower in WBA than in RUN (P < .05), indicating higher arterial distensibility along the arm. Mean arterial pressure was lower in ATH than in CTR and in RUN than in WBA (P < .05). Synthesized aortic augmentation index (AI@75) was lower among ATH than among CTR (-12.8 ± 1.6 vs -2.6 ± 1.2%, P < .001) and in WBA than in RUN (-16.4 ± 2.5 vs -10.7 ± 2.0%, P < .05), suggesting a diminished return of reflection waves to the aorta during systole. Carotid-femoral PWV and intima-media thickness (IMT), lumen diameter and radial distensibility of the CCA were similar in ATH and CTR. Elastic artery distensibility and carotid artery IMT are not different in young women with extensive endurance training over several years and in those with sedentary lifestyle. On the other hand, our data suggest that long-term endurance training is associated with potentially favourable peripheral artery adaptation, especially in sports where upper body work is added. This adaptation, if persisting later in life, could contribute to lower cardiovascular risk. © 2018 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

How can attosecond pulse train interferometry interrogate electron dynamics?

NASA Astrophysics Data System (ADS)

Arnold, C. L.; Isinger, M.; Busto, D.; Guénot, D.; Nandi, S.; Zhong, S.; Dahlström, J. M.; Gisselbrecht, M.; l'Huillier, A.

2018-04-01

Light pulses of sub-100 as (1 as=10-18 s) duration, with photon energies in the extreme-ultraviolet (XUV) spectral domain, represent the shortest event in time ever made and controlled by human beings. Their first experimental observation in 2001 has opened the door to investigating the fundamental dynamics of the quantum world on the natural time scale for electrons in atoms, molecules and solids and marks the beginning of the scientific field now called attosecond science.

Development of a High-Average-Power Compton Gamma Source for Lepton Colliders

NASA Astrophysics Data System (ADS)

Pogorelsky, Igor; Polyanskiy, Mikhail N.; Yakimenko, Vitaliy; Platonenko, Viktor T.

2009-01-01

Gamma- (γ-) ray beams of high average power and peak brightness are of demand for a number of applications in high-energy physics, material processing, medicine, etc. One of such examples is gamma conversion into polarized positrons and muons that is under consideration for projected lepton colliders. A γ-source based on the Compton backscattering from the relativistic electron beam is a promising candidate for this application. Our approach to the high-repetition γ-source assumes placing the Compton interaction point inside a CO2 laser cavity. A laser pulse interacts with periodical electron bunches on each round-trip inside the laser cavity producing the corresponding train of γ-pulses. The round-trip optical losses can be compensated by amplification in the active laser medium. The major challenge for this approach is in maintaining stable amplification rate for a picosecond CO2-laser pulse during multiple resonator round-trips without significant deterioration of its temporal and transverse profiles. Addressing this task, we elaborated on a computer code that allows identifying the directions and priorities in the development of such a multi-pass picosecond CO2 laser. Proof-of-principle experiments help to verify the model and show the viability of the concept. In these tests we demonstrated extended trains of picosecond CO2 laser pulses circulating inside the cavity that incorporates the Compton interaction point.

Too old to benefit from sports? The cardiovascular effects of exercise training in elderly subjects treated for isolated systolic hypertension.

PubMed

Westhoff, Timm H; Franke, Nadine; Schmidt, Sven; Vallbracht-Israng, Katja; Meissner, Romy; Yildirim, Havva; Schlattmann, Peter; Zidek, Walter; Dimeo, Fernando; van der Giet, Markus

2007-01-01

Hypertension in the elderly is commonly characterized by an elevation of pulse pressure. With regard to advanced arteriosclerosis and limited physical fitness, doubt was casted whether elderly patients still achieve relevant cardiovascular benefits by physical exercise. The present work examines the impact of pulse pressure as a footprint of vascular ageing on cardiovascular benefits of endurance training in elderly hypertensives. 54 patients > or =60 years with systolic 24-hour ambulatory blood pressure (ABP) >140 mm Hg and/or antihypertensive treatment and diastolic ABP < or =90 mm Hg were randomly assigned to sedentary activity or a 12-week treadmill exercise program (target lactate 2.5 +/- 0.5 mmol/l). Exercise significantly decreased systolic and diastolic ABP by 8.5 +/- 8.2 and 5.1 +/- 3.7 mm Hg (p < 0.001 each) and increased physical performance. Arterial compliance remained unchanged, whereas endothelium-dependent vasodilation--measured by flow-mediated dilation--significantly increased from 5.6 +/- 1.7 to 7.9 +/- 3.0% (p < 0.007). After adjustment for initial systolic ABP, pulse pressure did not affect the change of BP. The exercise-induced reduction of BP, which is mediated by improved endothelial function, is independent of pulse pressure. Thus, physical exercise is a helpful adjunct to control BP even in old hypertensives with markedly increased arterial stiffness. Copyright 2007 S. Karger AG, Basel.

Electron transfer processes occurring on platinum neural stimulating electrodes: pulsing experiments for cathodic-first/charge-balanced/biphasic pulses for 0.566 ≤ k ≤ 2.3 in oxygenated and deoxygenated sulfuric acid.

PubMed

Kumsa, Doe W; Montague, Fred W; Hudak, Eric M; Mortimer, J Thomas

2016-10-01

The application of a train of cathodic-first/charge-balanced/biphasic pulses applied to a platinum electrode resulted in a positive creep of the anodic phase potential that increases with increasing charge injection but reaches a steady-state value before 1000 pulses have been delivered. The increase follows from the fact that charge going into irreversible reactions occurring during the anodic phase must equal the charge going into irreversible reactions during the cathodic phase for charge-balanced pulses. In an oxygenated electrolyte the drift of the measured positive potential moved into the platinum oxidation region of the i(V e) profile when the charge injection level exceeds k = 1.75. Platinum dissolution may occur in this region and k = 1.75 defines a boundary between damaging and non-damaging levels on the Shannon Plot. In a very low oxygen environment, the positive potential remained below the platinum oxidation region for the highest charge injection values studied, k = 2.3. The results support the hypothesis that platinum dissolution is the defining factor for the Shannon limit, k = 1.75. Numerous instrumentation issues were encountered in the course of making measurements. The solutions to these issues are provided.

Device For Trapping Laser Pulses In An Optical Delay Line

DOEpatents

Yu, David U. L.; Bullock, Donald L.

1997-12-23

A device for maintaining a high-energy laser pulse within a recirculating optical delay line for a period time to optimize the interaction of the pulse with an electron beam pulse train comprising closely spaced electron micropulses. The delay line allows a single optical pulse to interact with many of the electron micropulses in a single electron beam macropulse in sequence and for the introduction of additional optical pulses to interact with the micropulses of additional electron beam macropulses. The device comprises a polarization-sensitive beam splitter for admitting an optical pulse to and ejecting it from the delay line according to its polarization state, a Pockels cell to control the polarization of the pulse within the delay line for the purpose of maintaining it within the delay line or ejecting it from the delay line, a pair of focusing mirrors positioned so that a collimated incoming optical pulse is focused by one of them to a focal point where the pulse interacts with the electron beam and then afterwards the pulse is recollimated by the second focusing mirror, and a timing device which synchronizes the introduction of the laser pulse into the optical delay line with the arrival of the electron macropulse at the delay line to ensure the interaction of the laser pulse with a prescribed number of electron micropulses in sequence. In a first embodiment of the invention, the principal optical elements are mounted with their axes collinear. In a second embodiment, all principal optical elements are mounted in the configuration of a ring.

Binaural electric-acoustic interactions recorded from the inferior colliculus of Guinea pigs: the effect of masking observed in the central nucleus of the inferior colliculus.

PubMed

Noh, Heil; Lee, Dong-Hee

2012-09-01

To investigate the electric-acoustic interactions within the inferior colliculus of guinea pigs and to observe how central masking appears in invasive neural recordings of the inferior colliculus (IC). A platinum-iridium wire was inserted to scala tympani through cochleostomy with a depth no greater than 1 mm for intracochlear stimulation of electric pulse train. A 5 mm 100 µm, single-shank, thin-film, penetrating recording probe was inserted perpendicularly to the surface of the IC in the coronal plane at an angle of 30-40° off the parasagittal plane with a depth of 2.0-2.5 mm. The peripheral and central masking effects were compared using electric pulse trains to the left ear and acoustic noise to the left ear (ipsilateral) and to the right ear (contralateral). Binaural acoustic stimuli were presented with different time delays and compared with combined electric and acoustic stimuli. The averaged evoked potentials and total spike numbers were measured using thin-film electrodes inserted into the central nucleus of the IC. Ipsilateral noise had more obvious effects on the electric response than did contralateral noise. Contralateral noise decreased slightly the response amplitude to the electric pulse train stimuli. Immediately after the onset of acoustic noise, the response pattern changed transiently with shorter response intervals. The effects of contralateral noise were evident at the beginning of the continuous noise. The total spike number decreased when the binaural stimuli reached the IC most simultaneously. These results suggest that central masking is quite different from peripheral masking and occurs within the binaural auditory system, and this study showed that the effect of masking could be observed in the IC recording. These effects are more evident and consistent with the psychophysical data from spike number analyses than with the previously reported gross potential data.

Theoretical and experimental investigation of the nonlinear dynamical trends of passively mode-locked quantum dot lasers

NASA Astrophysics Data System (ADS)

Raghunathan, Ravi

In recent years, passively mode-locked quantum dot lasers have shown great promise as compact, efficient and reliable pulsed sources of light for a range of precision and high performance applications, such as high bit-rate optical communications, diverse waveform generation, metrology, and clock distribution in high-performance computing (HPC) processors. For such applications, stable optical pulses with short picosecond pulse durations and multi-gigahertz repetition rates are required. In addition, a low pulse-to-pulse timing jitter is also necessary to prevent errors arising from the ambiguity between neighboring pulses. In order to optimize pulse quality in terms of optical characteristics such as pulse shape and pulse train behavior, as well as RF characteristics such as phase noise and timing jitter, understanding the nonlinear output dynamics of such devices is of critical importance, not only to get a sense of the regimes of operation where device output might be stable or unstable, but also to gain insight into the parameters that influence the output characteristics the most, and how they can be accessed and exploited to optimize design and performance for next generation applications. In this dissertation, theoretical and experimental studies have been combined to investigate the dynamical trends of two-section passively mode-locked quantum dot lasers. On the theoretical side, a novel numerical modeling scheme is presented as a powerful and versatile framework to study the nonlinear dynamics specific to a device, with device-specific parameters extracted over a range of operating conditions. The practical utility of this scheme is then demonstrated, first, in an analytical capability to interpret and explain dynamical trends observed in experiment, and subsequently, as a predictive tool to guide experiment to operate in a desired dynamical regime. Modeling results are compared to experimental findings where possible. Finally, optical feedback from an external reflector is experimentally studied as an additional control mechanism over the output dynamics of the device, and shown to enable invaluable insight into the behavior of the RF and optical spectra of the output. Together, the theoretical and experimental findings of this dissertation are shown to offer a systematic approach to understand, control and exploit the dynamical trends of passively mode-locked two-section quantum dot lasers.

Billion frames per second spectrum measurement for high-repetition-rate optical pulses based on time stretching technique

NASA Astrophysics Data System (ADS)

Furukawa, Hideaki; Makino, Takeshi; Asghari, Mohammad H.; Trinh, Paul; Jalali, Bahram; Wang, Xiaomin; Kobayashi, Tetsuya; Man, Wai S.; Tsang, Kwong Shing; Wada, Naoya

2017-02-01

Single-shot and long record length spectrum measurements of high-repetition-rate optical pulses are essential for research on nonlinear dynamics as well as for applications in sensing and communication. To achieve a continuous measurements we employ the Time Stretch Dispersive Fourier Transform. We show single-shot measurements of millions of sequential pulses at high repetition rate of 1 Giga spectra per second. Results were obtained using -100 ps/nm dispersive Fourier transform module and a 50 Gsample/s real-time digitizer of 16 GHz bandwidth. Single-shot spectroscopy of 1 GHz optical pulse train was achieved with the wavelength resolution of approximately 150 pm. This instrument is ideal for observation of complex nonlinear dynamics such as switching, mode locking and soliton dynamics in high repetition rate lasers.

Generation of spectrally stable continuous-wave emission and ns pulses with a peak power of 4 W using a distributed Bragg reflector laser and a ridge-waveguide power amplifier.

PubMed

Klehr, A; Wenzel, H; Fricke, J; Bugge, F; Erbert, G

2014-10-06

We have developed a diode-laser based master oscillator power amplifier (MOPA) light source which emits high-power spectrally stabilized and nearly-diffraction limited optical pulses in the nanoseconds range as required by many applications. The MOPA consists of a distributed Bragg reflector (DBR) laser as master oscillator driven by a constant current and a ridge waveguide power amplifier (PA) which can be driven by a constant current (DC) or by rectangular current pulses with a width of 5 ns at a repetition frequency of 200 kHz. Under pulsed operation the amplifier acts as an optical gate, converting the CW input beam emitted by the DBR laser into a train of short amplified optical pulses. With this experimental MOPA arrangement no relaxation oscillations occur. A continuous wave power of 1 W under DC injection and a pulse power of 4 W under pulsed operation are reached. For both operational modes the optical spectrum of the emission of the amplifier exhibits a peak at a constant wavelength of 973.5 nm with a spectral width < 10 pm.

Application of MEMS-based x-ray optics as tuneable nanosecond choppers

NASA Astrophysics Data System (ADS)

Chen, Pice; Walko, Donald A.; Jung, Il Woong; Li, Zhilong; Gao, Ya; Shenoy, Gopal K.; Lopez, Daniel; Wang, Jin

2017-08-01

Time-resolved synchrotron x-ray measurements often rely on using a mechanical chopper to isolate a set of x-ray pulses. We have started the development of micro electromechanical systems (MEMS)-based x-ray optics, as an alternate method to manipulate x-ray beams. In the application of x-ray pulse isolation, we recently achieved a pulse-picking time window of half a nanosecond, which is more than 100 times faster than mechanical choppers can achieve. The MEMS device consists of a comb-drive silicon micromirror, designed for efficiently diffracting an x-ray beam during oscillation. The MEMS devices were operated in Bragg geometry and their oscillation was synchronized to x-ray pulses, with a frequency matching subharmonics of the cycling frequency of x-ray pulses. The microscale structure of the silicon mirror in terms of the curvature and the quality of crystallinity ensures a narrow angular spread of the Bragg reflection. With the discussion of factors determining the diffractive time window, this report showed our approaches to narrow down the time window to half a nanosecond. The short diffractive time window will allow us to select single x-ray pulse out of a train of pulses from synchrotron radiation facilities.

Landscape self organisation: Modelling Sediment trains

NASA Astrophysics Data System (ADS)

Schoorl, J. M.; Temme, A. J. A. M.; Veldkamp, A.

2012-04-01

Rivers tend to develop towards an equilibrium length profile, independently of exogenous factors. In general, although still under debate, this so-called self-organisation is assumed to be caused by simple feedbacks between sedimentation and erosion. Erosion correlates positively with gradient and discharge and sedimentation negatively. With the LAPSUS model, which was run for the catchment of the Sabinal, a small river in the South of Spain, this interplay of erosion and sedimentation results in sediment pulses (sequences of incision and sedimentation through time). These pulses are visualised in a short movie ( see http://www.youtube.com/watch?v=V5LDUMvYZxU). In this case the LAPSUS model run did not take climate, base level nor tectonics into account. Therefore, these pulses can be considered independent of them. Furthermore, different scenarios show that the existence of the pulses is independent of precipitation, erodibility and sedimentation rate, although they control the number and shape of the pulses. A fieldwork check showed the plausibility of the occurrence of these sediment pulses. We conclude that the pulses as modelled with LAPSUS are indeed the consequence of the feedbacks between erosion and sedimentation and are not depending on exogenous factors. Keywords: Landscape self-organisation, Erosion, Deposition, LAPSUS, Modelling

Implementation of STUD Pulses at the Trident Laser and Initial Results

NASA Astrophysics Data System (ADS)

Johnson, R. P.; Shimada, T.; Montgomery, D. S.; Afeyan, B.; Hüller, S.

2012-10-01

Controlling and mitigating laser-plasma instabilities such as stimulated Brillouin scattering, stimulated Raman scattering, and crossed-beam energy transfer is important to achieve high-gain inertial fusion using laser drivers. Recent theory and simulations show that these instabilities can be largely controlled using laser pulses consisting of spike trains of uneven duration and delay (STUD) by modulating the laser on a picosecond time scale [1,2]. We have designed and implemented a STUD pulse generator at the LANL Trident Laser Facility using Fourier synthesis to produce a 0.5-ns envelope of psec-duration STUD pulses using a spatial light modulator. Initial results from laser propagation tests and measurements as well as initial laser-plasma characterization experiments will be presented.[4pt] [1] B. Afeyan and S. H"uller, ``Optimal Control of Laser Plasma Instabilities using STUD pulses,'' IFSA 2011, P.Mo.1, to appear in Euro. Phys. J. Web of Conf. (2012).[2] S. H"uller and B. Afeyan, ``Simulations of drastically reduced SBS with STUD pulses,'' IFSA 2011, O.Tu8-1, to appear in Euro. Phys. J. Web of Conf. (2012).

Laser Digital Cinema

NASA Astrophysics Data System (ADS)

Takeuchi, Eric B.; Flint, Graham W.; Bergstedt, Robert; Solone, Paul J.; Lee, Dicky; Moulton, Peter F.

2001-03-01

Electronic cinema projectors are being developed that use a digital micromirror device (DMDTM) to produce the image. Photera Technologies has developed a new architecture that produces truly digital imagery using discrete pulse trains of red, green, and blue light in combination with a DMDTM where in the number of pulses that are delivered to the screen during a given frame can be defined in a purely digital fashion. To achieve this, a pulsed RGB laser technology pioneered by Q-Peak is combined with a novel projection architecture that we refer to as Laser Digital CameraTM. This architecture provides imagery wherein, during the time interval of each frame, individual pixels on the screen receive between zero and 255 discrete pulses of each color; a circumstance which yields 24-bit color. Greater color depth, or increased frame rate is achievable by increasing the pulse rate of the laser. Additionally, in the context of multi-screen theaters, a similar architecture permits our synchronously pulsed RGB source to simultaneously power three screens in a color sequential manner; thereby providing an efficient use of photons, together with the simplifications which derive from using a single DMDTM chip in each projector.

Introduction of paramedic led Echo in Life Support into the pre-hospital environment: The PUCA study.

PubMed

Reed, Matthew J; Gibson, Louise; Dewar, Alistair; Short, Steven; Black, Polly; Clegg, Gareth R

2017-03-01

Can pre-hospital paramedic responders perform satisfactory pre-hospital Echo in Life Support (ELS) during the 10-s pulse check window, and does pre-hospital ELS adversely affect the delivery of cardiac arrest care. Prospective observational study of a cohort of ELS trained paramedics using saved ultrasound clips and wearable camera videos. Between 23rd June 2014 and 31st January 2016, seven Resuscitation Rapid Response Unit (3RU) paramedics attended 45 patients in Lothian suffering out-of-hospital CA where resuscitation was attempted and ELS was available and performed. 80% of first ELS attempts by paramedics produced an adequate view which was excellent/good or satisfactory in 68%. 44% of views were obtained within the 10-s pulse check window with a median time off the chest of 17 (IQR 13-20) seconds. A decision to perform ELS was communicated 67% of the time, and the 10-s pulse check was counted aloud in 60%. A manual pulse check was observed in around a quarter of patients and the rhythm on the monitor was checked 38% of the time. All decision changing scans involved a decision to stop resuscitation. Paramedics are able to obtain good ELS views in the pre-hospital environment but this may lead to longer hands off the chest time and possibly less pulse and monitor checking than is recommended. Future studies will need to demonstrate either improved outcomes or a benefit from identifying patients in whom further resuscitation and transportation is futile, before ELS is widely adopted in most pre-hospital systems. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Airborne Laser Scanning of Forest Stem Volume in a Mountainous Environment

PubMed Central

Hollaus, Markus; Wagner, Wolfgang; Maier, Bernhard; Schadauer, Klemens

2007-01-01

Airborne laser scanning (ALS) is an active remote sensing technique that uses the time-of-flight measurement principle to capture the three-dimensional structure of the earth's surface with pulsed lasers that transmit nanosecond-long laser pulses with a high pulse repetition frequency. Over forested areas most of the laser pulses are reflected by the leaves and branches of the trees, but a certain fraction of the laser pulses reaches the forest floor through small gaps in the canopy. Thus it is possible to reconstruct both the three-dimensional structure of the forest canopy and the terrain surface. For the retrieval of quantitative forest parameters such as stem volume or biomass it is necessary to use models that combine ALS with inventory data. One approach is to use multiplicative regression models that are trained with local inventory data. This method has been widely applied over boreal forest regions, but so far little experience exists with applying this method for mapping alpine forest. In this study the transferability of this approach to a 128 km2 large mountainous region in Vorarlberg, Austria, was evaluated. For the calibration of the model, inventory data as operationally collected by Austrian foresters were used. Despite these inventory data are based on variable sample plot sizes, they could be used for mapping stem volume for the entire alpine study area. The coefficient of determination R2 was 0.85 and the root mean square error (RMSE) 90.9 m3ha−1 (relative error of 21.4%) which is comparable to results of ALS studies conducted over topographically less complex environments. Due to the increasing availability, ALS data could become an operational part of Austrian's forest inventories.

Attosecond polarization control in atomic RABBITT-like experiments assisted by a circularly polarized laser

NASA Astrophysics Data System (ADS)

Boll, D. I. R.; Fojón, O. A.

2017-12-01

We study theoretically the single ionization of noble gas atoms by the combined action of an attosecond pulse train with linear polarization and an assistant laser field with circular polarization. We employ a non-perturbative model that under certain approximations gives closed-form expressions for the angular distributions of photoelectrons. Interestingly, our model allow us to interpret these angular distributions as two-centre interferences where the orientation and the modulus of the separation vector between the virtual emitters is governed by the assistant laser field. Additionally, we show that such a configuration of light fields is similar to the polarization control technique, where both the attosecond pulse train and the assistant laser field have linear polarizations whose relative orientation may be controlled. Moreover, in order to compare our results with the available experimental data, we obtain analytical expressions for the cross sections integrated over the photoelectron emission angles. By means of these expressions, we define the ‘magic time’ as the delay for which the total cross sections for atomic targets exhibit the same functional form as the one of the monochromatic photoionization of diatomic molecular targets.

Effect of signal jitter on the spectrum of rotor impulsive noise

NASA Technical Reports Server (NTRS)

Brooks, Thomas F.

1987-01-01

The effect of randomness or jitter of the acoustic waveform on the spectrum of rotor impulsive noise is studied because of its importance for data interpretation. An acoustic waveform train is modelled representing rotor impulsive noise. The amplitude, shape, and period between occurrences of individual pulses are allowed to be randomized assuming normal probability distributions. Results, in terms of the standard deviations of the variable quantities, are given for the autospectrum as well as special processed spectra designed to separate harmonic and broadband rotor noise components. Consideration is given to the effect of accuracy in triggering or keying to a rotor one per revolution signal. An example is given showing the resultant spectral smearing at the high frequencies due to the pulse signal period variability.

Effect of signal jitter on the spectrum of rotor impulsive noise

NASA Technical Reports Server (NTRS)

Brooks, Thomas F.

1988-01-01

The effect of randomness or jitter of the acoustic waveform on the spectrum of rotor impulsive noise is studied because of its importance for data interpretation. An acoustic waveform train is modeled representing rotor impulsive noise. The amplitude, shape, and period between occurrences of individual pulses are allowed to be randomized assuming normal probability distributions. Results, in terms of the standard deviations of the variable quantities, are given for the autospectrum as well as special processed spectra designed to separate harmonic and broadband rotor noise components. Consideration is given to the effect of accuracy in triggering or keying to a rotor one per revolution signal. An example is given showing the resultant spectral smearing at the high frequencies due to the pulse signal period variability.

212-Angstrom neonlike zinc laser of LULI

NASA Astrophysics Data System (ADS)

Jamelot, Gerard; Jaegle, Pierre; Rus, Bedrich; Carillon, Antoine; Klisnick, Annie; Nantel, Marc; Sebban, Stephane; Albert, F.; Zeitoun, Philippe; Plankl, E.; Sirgand, A.; Lewis, Ciaran L. S.; MacPhee, Andrew G.; Tallents, Gregory J.; Krishnan, J.; Holden, M.

1995-09-01

The main feature of x-ray laser research at LULI is the development of a saturated laser at 212 angstrom with a relatively small pump laser of 0.4 kJ in 600 ps. The laser works with the 3p- 3s J equals O yields 1 transition of neon-like zinc, by using the double-pass of amplified radiation in the active medium. Plasma parameters (temperature, density, homogeneity), and x-ray laser emission properties (intensity, pointing angle, divergence, and coherence) have been studied. Lasing action needs the main laser pulse to be preceded by a ten-prepulse train (contrast ratio less than 103) due to the remnant oscillator. The effect of a single prepulse was investigated as a function of contrast ratio and delay between the prepulse and the main pulse.

A Tesla-pulse forming line-plasma opening switch pulsed power generator.

PubMed

Novac, B M; Kumar, R; Smith, I R

2010-10-01

A pulsed power generator based on a high-voltage Tesla transformer which charges a 3.85 Ω/55 ns water-filled pulse forming line to 300 kV has been developed at Loughborough University as a training tool for pulsed power students. The generator uses all forms of insulation specific to pulsed power technology, liquid (oil and water), gas (SF(6)), and magnetic insulation in vacuum, and a number of fast voltage and current sensors are implemented for diagnostic purposes. A miniature (centimeter-size) plasma opening switch has recently been coupled to the output of the pulse forming line, with the overall system comprising the first phase of a program aimed at the development of a novel repetitive, table-top generator capable of producing 15 GW pulses for high power microwave loads. Technical details of all the generator components and the main experimental results obtained during the program and demonstrations of their performance are presented in the paper, together with a description of the various diagnostic tools involved. In particular, it is shown that the miniature plasma opening switch is capable of reducing the rise time of the input current while significantly increasing the load power. Future plans are outlined in the conclusions.

Effects of fish size and temperature on weakfish disturbance calls: implications for the mechanism of sound generation.

PubMed

Connaughton, M A; Taylor, M H; Fine, M L

2000-05-01

To categorize variation in disturbance calls of the weakfish Cynoscion regalis and to understand their generation, we recorded sounds produced by different-sized fish, and by similar-sized fish at different temperatures, as well as muscle electromyograms. Single, simultaneous twitches of the bilateral sonic muscles produce a single sound pulse consisting of a two- to three-cycle acoustic waveform. Typical disturbance calls at 18 degrees C consist of trains of 2-15 pulses with a sound pressure level (SPL) of 74 dB re 20 microPa at 10 cm, a peak frequency of 540 Hz, a repetition rate of 20 Hz and a pulse duration of 3.5 ms. The pulse duration suggests an incredibly short twitch time. Sound pressure level (SPL) and pulse duration increase and dominant frequency decreases in larger fish, whereas SPL, repetition rate and dominant frequency increase and pulse duration decreases with increasing temperature. The dominant frequency is inversely related to pulse duration and appears to be determined by the duration of muscle contraction. We suggest that the lower dominant frequency of larger fish is caused by a longer pulse (=longer muscle twitch) and not by the lower resonant frequency of a larger swimbladder.

Different evolution dynamics of vector solitons depending on their polarization states

NASA Astrophysics Data System (ADS)

Chen, Wei-Cheng; Chen, Guo-Jie

2014-03-01

There are three types of temporal evolution dynamics of vector solitons observed in a ring fiber laser with a semiconductor saturable absorption mirror (SESAM) as a mode-locker. It is found that the polarization property of vector solitons is an important factor for achieving different evolution dynamics. The vector soliton with a uniform polarization state across the whole pulse profile and zero polarization extinction ratio operates at a fundamental repetition rate with a single pulse profile. The elliptically polarized vector soliton with a larger polarization extinction ratio exhibits a harmonic pulse train. The soliton bunching with multi-peak structures exists between the above two states and shows elliptical polarization with a small polarization extinction ratio.

Passive Q-switching of ˜2.7 µm Er:Lu2O3 ceramic laser with a semiconductor saturable absorber mirror

NASA Astrophysics Data System (ADS)

Ren, Xiaojing; Shen, Deyuan; Zhang, Jian; Tang, Dingyuan

2018-02-01

We demonstrate the passively Q-switched operation of an Er:Lu2O3 ceramic laser at ˜2.7 µm for the first time, to the best of our knowledge. By using a semiconductor saturable absorber mirror (SESAM), stable pulse trains with a repetition rate of 20-33.3 kHz are produced in a compacted v-shaped resonator. The pulse duration (FWHM), pulse energy, and peak power are 660 ns, 1.8 µJ, and ˜2.73 W, respectively, at 33.3 kHz repetition rate. Prospects for further improvements in terms of laser performances are discussed.

Bright attosecond γ-ray pulses from nonlinear Compton scattering with laser-illuminated compound targets

NASA Astrophysics Data System (ADS)

Zhu, Xing-Long; Chen, Min; Yu, Tong-Pu; Weng, Su-Ming; Hu, Li-Xiang; McKenna, Paul; Sheng, Zheng-Ming

2018-04-01

Attosecond light sources have the potential to open up totally unexplored research avenues in ultrafast science. However, the photon energies achievable using existing generation schemes are limited to the keV range. Here, we propose and numerically demonstrate an all-optical mechanism for the generation of bright MeV attosecond γ-photon beams with desirable angular momentum. Using a circularly polarized Laguerre-Gaussian laser pulse focused onto a cone-foil target, dense attosecond bunches ( ≲ 170 as ) of electrons are produced. The electrons interact with the laser pulse which is reflected by a plasma mirror, producing ultra-brilliant (˜1023 photons/s/mm2/mrad2/0.1%BW) multi-MeV (Eγ,max > 30 MeV) isolated attosecond ( ≲ 260 as ) γ-ray pulse trains. Moreover, the angular momentum is transferred to γ-photon beams via nonlinear Compton scattering of ultra-intense tightly focused laser pulse by energetic electrons. Such a brilliant attosecond γ-photon source would provide the possibilities in attosecond nuclear science.

Bright high-order harmonic generation with controllable polarization from a relativistic plasma mirror

PubMed Central

Chen, Zi-Yu; Pukhov, Alexander

2016-01-01

Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order harmonic generation from noble gases. Here we propose and numerically demonstrate a laser–plasma scheme to generate bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The harmonic polarization state is fully controlled by the laser–plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047

High passive CEP stability from a few-cycle, tunable NOPA-DFG system for observation of CEP-effects in photoemission.

PubMed

Vogelsang, Jan; Robin, Jörg; Piglosiewicz, Björn; Manzoni, Cristian; Farinello, Paolo; Melzer, Stefan; Feru, Philippe; Cerullo, Giulio; Lienau, Christoph; Groß, Petra

2014-10-20

The investigation of fundamental mechanisms taking place on a femtosecond time scale is enabled by ultrafast pulsed laser sources. Here, the control of pulse duration, center wavelength, and especially the carrier-envelope phase has been shown to be of essential importance for coherent control of high harmonic generation and attosecond physics and, more recently, also for electron photoemission from metallic nanostructures. In this paper we demonstrate the realization of a source of 2-cycle laser pulses tunable between 1.2 and 2.1 μm, and with intrinsic CEP stability. The latter is guaranteed by difference frequency generation between the output pulse trains of two noncollinear optical parametric amplifier stages that share the same CEP variations. The CEP stability is better than 50 mrad over 20 minutes, when averaging over 100 pulses. We demonstrate the good CEP stability by measuring kinetic energy spectra of photoemitted electrons from a single metal nanostructure and by observing a clear variation of the electron yield with the CEP.

Time transfer between the Goddard Optical Research Facility and the U.S. Naval Observatory using 100 picosecond laser pulses

NASA Technical Reports Server (NTRS)

Alley, C. O.; Rayner, J. D.; Steggerda, C. A.; Mullendore, J. V.; Small, L.; Wagner, S.

1983-01-01

A horizontal two-way time comparison link in air between the University of Maryland laser ranging and time transfer equipment at the Goddard Optical Research Facility (GORF) 1.2 m telescope and the Time Services Division of the U.S. Naval Observatory (USNO) was established. Flat mirrors of 25 cm and 30 cm diameter respectively were placed on top of the Washington Cathedral and on a water tower at the Beltsville Agricultural Research Center. Two optical corner reflectors at the USNO reflect the laser pulses back to the GORF. Light pulses of 100 ps duration and an energy of several hundred microjoules are sent at the rate of 10 pulses per second. The detection at the USNO is by means of an RCA C30902E avalanche photodiode and the timing is accomplished by an HP 5370A computing counter and an HP 1000 computer with respect to a 10 pps pulse train from the Master Clock.