Evaluating intervention fidelity: an example from a high-intensity interval training study.

PubMed

Taylor, Kathryn L; Weston, Matthew; Batterham, Alan M

2015-01-01

Intervention fidelity refers to the degree to which an experimental manipulation has been implemented as intended, but simple, robust methods for quantifying fidelity have not been well documented. Therefore, we aim to illustrate a rigorous quantitative evaluation of intervention fidelity, using data collected during a high-intensity interval training intervention. Single-group measurement study. Seventeen adolescents (mean age ± standard deviation [SD] 14.0 ± 0.3 years) attended a 10-week high-intensity interval training intervention, comprising two exercise sessions per week. Sessions consisted of 4-7 45-s maximal effort repetitions, interspersed with 90-s rest. We collected heart rate data at 5-s intervals and recorded the peak heart rate for each repetition. The high-intensity exercise criterion was ≥ 90% of individual maximal heart rate. For each participant, we calculated the proportion of total exercise repetitions exceeding this threshold. A linear mixed model was applied to properly separate the variability in peak heart rate between- and within-subjects. Results are presented both as intention to treat (including missed sessions) and per protocol (only participants with 100% attendance; n=8). For intention to treat, the median (interquartile range) proportion of repetitions meeting the high-intensity criterion was 58% (42% to 68%). The mean peak heart rate was 85% of maximal, with a between-subject SD of 7.8 (95% confidence interval 5.4 to 11.3) percentage points and a within-subject SD of 15.1 (14.6 to 15.6) percentage points. For the per protocol analysis, the median proportion of high-intensity repetitions was 68% (47% to 86%). The mean peak heart rate was 91% of maximal, with between- and within-subject SDs of 3.1 (-1.3 to 4.6) and 3.4 (3.2 to 3.6) percentage points, respectively. Synthesising information on exercise session attendance and compliance (exercise intensity) quantifies the intervention dose and informs evaluations of treatment fidelity.

Variability in spatio-temporal pattern of trapezius activity and coordination of hand-arm muscles during a sustained repetitive dynamic task.

PubMed

Samani, Afshin; Srinivasan, Divya; Mathiassen, Svend Erik; Madeleine, Pascal

2017-02-01

The spatio-temporal distribution of muscle activity has been suggested to be a determinant of fatigue development. Pursuing this hypothesis, we investigated the pattern of muscular activity in the shoulder and arm during a repetitive dynamic task performed until participants' rating of perceived exertion reached 8 on Borg's CR-10 scale. We collected high-density surface electromyogram (HD-EMG) over the upper trapezius, as well as bipolar EMG from biceps brachii, triceps brachii, deltoideus anterior, serratus anterior, upper and lower trapezius from 21 healthy women. Root-mean-square (RMS) and mean power frequency (MNF) were calculated for all EMG signals. The barycenter of RMS values over the HD-EMG grid was also determined, as well as normalized mutual information (NMI) for each pair of muscles. Cycle-to-cycle variability of these metrics was also assessed. With time, EMG RMS increased for most of the muscles, and MNF decreased. Trapezius activity became higher on the lateral side than on the medial side of the HD-EMG grid and the barycenter moved in a lateral direction. NMI between muscle pairs increased with time while its variability decreased. The variability of the metrics during the initial 10 % of task performance was not associated with the time to task termination. Our results suggest that the considerable variability in force and posture contained in the dynamic task per se masks any possible effects of differences between subjects in initial motor variability on the rate of fatigue development.

Performance Variability as a Predictor of Response to Aphasia Treatment.

PubMed

Duncan, E Susan; Schmah, Tanya; Small, Steven L

2016-10-01

Performance variability in individuals with aphasia is typically regarded as a nuisance factor complicating assessment and treatment. We present the alternative hypothesis that intraindividual variability represents a fundamental characteristic of an individual's functioning and an important biomarker for therapeutic selection and prognosis. A total of 19 individuals with chronic aphasia participated in a 6-week trial of imitation-based speech therapy. We assessed improvement both on overall language functioning and repetition ability. Furthermore, we determined which pretreatment variables best predicted improvement on the repetition test. Significant gains were made on the Western Aphasia Battery-Revised (WAB) Aphasia Quotient, Cortical Quotient, and 2 subtests as well as on a separate repetition test. Using stepwise regression, we found that pretreatment intraindividual variability was the only predictor of improvement in performance on the repetition test, with greater pretreatment variability predicting greater improvement. Furthermore, the degree of reduction in this variability over the course of treatment was positively correlated with the degree of improvement. Intraindividual variability may be indicative of potential for improvement on a given task, with more uniform performance suggesting functioning at or near peak potential. © The Author(s) 2016.

Knee Pain during Strength Training Shortly following Fast-Track Total Knee Arthroplasty: A Cross-Sectional Study

PubMed Central

Bandholm, Thomas; Thorborg, Kristian; Lunn, Troels Haxholdt; Kehlet, Henrik; Jakobsen, Thomas Linding

2014-01-01

Background Loading and contraction failure (muscular exhaustion) are strength training variables known to influence neural activation of the exercising muscle in healthy subjects, which may help reduce neural inhibition of the quadriceps muscle following total knee arthroplasty (TKA). It is unknown how these exercise variables influence knee pain after TKA. Objective To investigate the effect of loading and contraction failure on knee pain during strength training, shortly following TKA. Design Cross-sectional study. Setting Consecutive sample of patients from the Copenhagen area, Denmark, receiving a TKA, between November 2012 and April 2013. Participants Seventeen patients, no more than 3 weeks after their TKA. Main outcome measures: In a randomized order, the patients performed 1 set of 4 standardized knee extensions, using relative loads of 8, 14, and 20 repetition maximum (RM), and ended with 1 single set to contraction failure (14 RM load). The individual loadings (kilograms) were determined during a familiarization session >72 hours prior. The patients rated their knee pain during each repetition, using a numerical rating scale (0–10). Results Two patients were lost to follow up. Knee pain increased with increasing load (20 RM: 3.1±2.0 points, 14 RM: 3.5±1.8 points, 8 RM: 4.3±2.5 points, P = 0.006), and repetitions to contraction failure (10% failure: 3.2±1.9 points, 100% failure: 5.4±1.6 points, P<0.001). Resting knee pain 60 seconds after the final repetition (2.7±2.4 points) was not different from that recorded before strength training (2.7±1.8 points, P = 0.88). Conclusion Both loading and repetitions performed to contraction failure during knee- extension strength-training, increased post-operative knee pain during strength training implemented shortly following TKA. However, only the increase in pain during repetitions to contraction failure exceeded that defined as clinically relevant, and was very short-lived. Trial Registration ClinicalTrials.gov NCT01729520 PMID:24614574

Effects of a cognitive dual task on variability and local dynamic stability in sustained repetitive arm movements using principal component analysis: a pilot study.

PubMed

Longo, Alessia; Federolf, Peter; Haid, Thomas; Meulenbroek, Ruud

2018-06-01

In many daily jobs, repetitive arm movements are performed for extended periods of time under continuous cognitive demands. Even highly monotonous tasks exhibit an inherent motor variability and subtle fluctuations in movement stability. Variability and stability are different aspects of system dynamics, whose magnitude may be further affected by a cognitive load. Thus, the aim of the study was to explore and compare the effects of a cognitive dual task on the variability and local dynamic stability in a repetitive bimanual task. Thirteen healthy volunteers performed the repetitive motor task with and without a concurrent cognitive task of counting aloud backwards in multiples of three. Upper-body 3D kinematics were collected and postural reconfigurations-the variability related to the volunteer's postural change-were determined through a principal component analysis-based procedure. Subsequently, the most salient component was selected for the analysis of (1) cycle-to-cycle spatial and temporal variability, and (2) local dynamic stability as reflected by the largest Lyapunov exponent. Finally, end-point variability was evaluated as a control measure. The dual cognitive task proved to increase the temporal variability and reduce the local dynamic stability, marginally decrease endpoint variability, and substantially lower the incidence of postural reconfigurations. Particularly, the latter effect is considered to be relevant for the prevention of work-related musculoskeletal disorders since reduced variability in sustained repetitive tasks might increase the risk of overuse injuries.

Metacognitive monitoring during category learning: how success affects future behaviour.

PubMed

Doyle, Mario E; Hourihan, Kathleen L

2016-10-01

The purpose of this study was to see how people perceive their own learning during a category learning task, and whether their perceptions matched their performance. In two experiments, participants were asked to learn natural categories, of both high and low variability, and make category learning judgements (CLJs). Variability was manipulated by varying the number of exemplars and the number of times each exemplar was presented within each category. Experiment 1 showed that participants were generally overconfident in their knowledge of low variability families, suggesting that they considered repetition to be more useful for learning than it actually was. Also, a correct trial, for a particular category, was more likely to occur if the previous trial was correct. CLJs had the largest increase when a trial was correct following an incorrect trial and the largest decrease when an incorrect trial followed a correct trial. Experiment 2 replicated these results, but also demonstrated that global CLJ ratings showed the same bias towards repetition. These results indicate that we generally identify success as being the biggest determinant of learning, but do not always recognise cues, such as variability, that enhance learning.

Isokinetic Dynamometry in Healthy Versus Sarcopenic and Malnourished Elderly: Beyond Simple Measurements of Muscle Strength.

PubMed

Cramer, Joel T; Jenkins, Nathaniel D M; Mustad, Vikkie A; Weir, Joseph P

2017-06-01

This study quantified systematic and intraindividual variability among three repetitions of concentric isokinetic knee extension and flexion tests to determine velocity-related differences in peak torque (PT) and mean power (MP) in healthy elderly (HE) versus sarcopenic and malnourished elderly (SME). In total, 107 HE ( n = 54 men, n = 53 women) and 261 SME ( n = 101 men, n = 160 women) performed three maximal concentric isokinetic knee extension and flexion repetitions at 60°·s -1 and 180°·s -1 . PT for Repetition 3 was lower than Repetitions 1 and 2, while MP for Repetition 1 was lower than Repetitions 2 and 3 in SME. Intraindividual variability among repetitions was correlated with strength, but not age, and was greater in SME, during knee flexion, and at 180°·s -1 . Velocity-related decreases in PT from 60°·s -1 to 180°·s -1 were more pronounced in SME. In summary, (a) the repetition with the highest PT value may be the best indicator of maximal strength, while the average may indicate strength maintenance in SME; (b) intraindividual variability among repetitions reflects functional decrements from HE to SME; and (c) decreases in PT from 60°·s to 180°·s may reflect greater losses of fast-twitch (type II) fiber function.

Efficacy Of The Repetitions In Reserve-Based Rating Of Perceived Exertion For The Bench Press In Experienced And Novice Benchers.

PubMed

Ormsbee, Michael J; Carzoli, Joseph P; Klemp, Alex; Allman, Brittany R; Zourdos, Michael C; Kim, Jeong-Su; Panton, Lynn B

2017-03-13

Autoregulation (AR) is the practice of adjusting training variables in response to athlete feedback. One component of AR postulated to enhance resistance training adaptations involves implementing a resistance training-specific rating of perceived exertion (RPE) scale measuring repetitions in reserve (RIR). The purpose of this study was to examine the efficacy of this method using the bench press exercise. Twenty-seven college-aged men were assigned to one of two groups based upon training age: experience benchers (EB) (n=14, training age: 4.7±2.0 yrs) and novice benchers (NB) (n=13, training age: 1.1±0.6 yrs). Subjects performed one-repetition maximum (1RM) followed by single-repetition sets with loads corresponding to 60, 75, and 90% of 1RM and an 8-repetition set at 70% 1RM. Subjects reported a corresponding RPE, based on RIR, for every set. Average velocity was recorded for each single-repetition set along with the first and last repetitions of the 8-repetition set at 70% 1RM. Average velocity at 100% of 1RM in EB was slower (0.14±0.04 m[BULLET OPERATOR]s) compared to NB (0.20±0.05 m[BULLET OPERATOR]s) (p<0.001). EB recorded greater RPE than NB at 1RM (EB: 9.86±0.14 vs. NB: 9.35±0.36) (p=0.011). No between-group differences existed for average velocity or RPE at any other intensity. Both EB (r=0.85, p<0.001) and NB (r=0.85, p<0.001) had strong inverse significant correlations between average velocity and RPE at all intensities. Our findings suggest that the RIR-based RPE scale may be an efficacious approach for AR of bench press training load and volume in college-aged men.

Fast repetition rate (FRR) fluorometer and method for measuring fluorescence and photosynthetic parameters

DOEpatents

Kolber, Zbigniew; Falkowski, Paul

1995-06-20

A fast repetition rate fluorometer device and method for measuring in vivo fluorescence of phytoplankton or higher plants chlorophyll and photosynthetic parameters of phytoplankton or higher plants by illuminating the phytoplankton or higher plants with a series of fast repetition rate excitation flashes effective to bring about and measure resultant changes in fluorescence yield of their Photosystem II. The series of fast repetition rate excitation flashes has a predetermined energy per flash and a rate greater than 10,000 Hz. Also, disclosed is a flasher circuit for producing the series of fast repetition rate flashes.

Generation of 103 fs mode-locked pulses by a gain linewidth-variable Nd,Y:CaF2 disordered crystal.

PubMed

Qin, Z P; Xie, G Q; Ma, J; Ge, W Y; Yuan, P; Qian, L J; Su, L B; Jiang, D P; Ma, F K; Zhang, Q; Cao, Y X; Xu, J

2014-04-01

We have demonstrated a diode-pumped passively mode-locked femtosecond Nd,Y:CaF2 disordered crystal laser for the first time to our knowledge. By choosing appropriate Y-doping concentration, a broad fluorescence linewidth of 31 nm has been obtained from the gain linewidth-variable Nd,Y:CaF2 crystal. With the Nd,Y:CaF2 disordered crystal as gain medium, the mode-locked laser generated pulses with pulse duration as short as 103 fs, average output power of 89 mW, and repetition rate of 100 MHz. To our best knowledge, this is the shortest pulse generated from Nd-doped crystal lasers so far. The research results show that the Nd,Y:CaF2 disordered crystal will be a potential alternative as gain medium of repetitive chirped pulse amplification for high-peak-power lasers.

Post-task Effects on EEG Brain Activity Differ for Various Differential Learning and Contextual Interference Protocols

PubMed Central

Henz, Diana; John, Alexander; Merz, Christian; Schöllhorn, Wolfgang I.

2018-01-01

A large body of research has shown superior learning rates in variable practice compared to repetitive practice. More specifically, this has been demonstrated in the contextual interference (CI) and in the differential learning (DL) approach that are both representatives of variable practice. Behavioral studies have indicate different learning processes in CI and DL. Aim of the present study was to examine immediate post-task effects on electroencephalographic (EEG) brain activation patterns after CI and DL protocols that reveal underlying neural processes at the early stage of motor consolidation. Additionally, we tested two DL protocols (gradual DL, chaotic DL) to examine the effect of different degrees of stochastic fluctuations within the DL approach with a low degree of fluctuations in gradual DL and a high degree of fluctuations in chaotic DL. Twenty-two subjects performed badminton serves according to three variable practice protocols (CI, gradual DL, chaotic DL), and a repetitive learning protocol in a within-subjects design. Spontaneous EEG activity was measured before, and immediately after each 20-min practice session from 19 electrodes. Results showed distinguishable neural processes after CI, DL, and repetitive learning. Increases in EEG theta and alpha power were obtained in somatosensory regions (electrodes P3, P7, Pz, P4, P8) in both DL conditions compared to CI, and repetitive learning. Increases in theta and alpha activity in motor areas (electrodes C3, Cz, C4) were found after chaotic DL compared to gradual DL, and CI. Anterior areas (electrodes F3, F7, Fz, F4, F8) showed increased activity in the beta and gamma bands after CI. Alpha activity was increased in occipital areas (electrodes O1, O2) after repetitive learning. Post-task EEG brain activation patterns suggest that DL stimulates the somatosensory and motor system, and engages more regions of the cortex than repetitive learning due to a tighter stimulation of the motor and somatosensory system during DL practice. CI seems to activate specifically executively controlled processing in anterior brain areas. We discuss the obtained patterns of post-training EEG traces as evidence for different underlying neural processes in CI, DL, and repetitive learning at the early stage of motor learning. PMID:29445334

Repetition rate dependency of low-density plasma effects during femtosecond-laser-based surgery of biological tissue

NASA Astrophysics Data System (ADS)

Kuetemeyer, K.; Baumgart, J.; Lubatschowski, H.; Heisterkamp, A.

2009-11-01

Femtosecond laser based nanosurgery of biological tissue is usually done in two different regimes. Depending on the application, low kHz repetition rates above the optical breakdown threshold or high MHz repetition rates in the low-density plasma regime are used. In contrast to the well understood optical breakdown, mechanisms leading to dissection below this threshold are not well known due to the complexity of chemical effects with high numbers of interacting molecules. Furthermore, the laser repetition rate may influence their efficiency. In this paper, we present our study on low-density plasma effects in biological tissue depending on repetition rate by static exposure of porcine corneal stroma to femtosecond pulses. We observed a continuous increase of the laser-induced damage with decreasing repetition rate over two orders of magnitude at constant numbers of applied laser pulses or constant laser pulse energies. Therefore, low repetition rates in the kHz regime are advantageous to minimize the total delivered energy to biological tissue during femtosecond laser irradiation. However, due to frequent excessive damage in this regime directly above the threshold, MHz repetition rates are preferable to create nanometer-sized cuts in the low-density plasma regime.

SU-E-T-460: Impact of the LINAC Repetition Rate On a High-Resolution Liquid Ionization Chamber Array for Patient-Specific QA

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

Wang, S; Driewer, J; Zheng, D

2015-06-15

Purpose: The purpose of this study is to investigate the LINAC repetition-rate (dose-rate) dependence of OCTAVIUS 1000SRS liquid ionization chamber (LIC) array for patient specific QA of SRT plans delivered with flattening-filter-free (FFF) beams. Methods: 1) The repetition-rate dependence of 1000SRS was measured in a phantom constructed with 5-cm solid water above and below the array for build-up and backscatter. A 0.3cc calibrated ion chamber was also placed along the central axis 2.3cm below the center chamber of the array for normalizing LINAC output fluctuation. The signals from the center chamber of the array under different repetition rates in themore » range of 400–2400 MU/min for 6xFFF and 10xFFF beams on a Varian TrueBeamSTx LINAC, normalized by the independent chamber readings, were analyzed for the array response dependence on repetition rates. 2) Twelve Step-and-shoot IMRS QA plans (6xFFF and 10xFFF) were delivered to the array under different repetition rates for analysis and comparison. 3) The absolute doses measured by the center chamber were compared to measurements using an independent ionization chamber with the identical setup, taken as the gold standard. 4) The correction factors based on the actual delivery repetition rate were applied to the measurements, and the results were compared again to the gold standard. Results: 1) The 1000SRS array exhibited repetition-rate dependence for FFF beams, up to 5% for 6xFFF and 10% for 10xFFF; 2) The array showed clinically-acceptable repetition-rate dependence for regular flattened beams; 3) This repetition-rate dependence significantly affected the measurement accuracy, thereby affecting IMRS QA results; 4) By applying an empirical repetition-rate correction, the corrected measurements agreed better with the gold standard ion chamber measurements. Conclusion: OCTAVIUS 1000SRS LIC array exhibited considerable repetition-rate dependence for FFF beams, which will affect the accuracy of the absolute QA measurements, especially for IMRS plans with the step-and-shoot technique.« less

Generation of µW level plateau harmonics at high repetition rate.

PubMed

Hädrich, S; Krebs, M; Rothhardt, J; Carstens, H; Demmler, S; Limpert, J; Tünnermann, A

2011-09-26

The process of high harmonic generation allows for coherent transfer of infrared laser light to the extreme ultraviolet spectral range opening a variety of applications. The low conversion efficiency of this process calls for optimization or higher repetition rate intense ultrashort pulse lasers. Here we present state-of-the-art fiber laser systems for the generation of high harmonics up to 1 MHz repetition rate. We perform measurements of the average power with a calibrated spectrometer and achieved µW harmonics between 45 nm and 61 nm (H23-H17) at a repetition rate of 50 kHz. Additionally, we show the potential for few-cycle pulses at high average power and repetition rate that may enable water-window harmonics at unprecedented repetition rate. © 2011 Optical Society of America

Variable Thickness Liquid Crystal Films for High Repetition Rate Laser Applications

NASA Astrophysics Data System (ADS)

Poole, Patrick; Willis, Christopher; Cochran, Ginevra; Hanna, Randall; Andereck, C. David; Schumacher, Douglass

2015-05-01

The presentation of a clean target or target substrate at high repetition rates is of importance to a number of photoelectron spectroscopy and free electron laser applications, often in high vacuum environments. Additionally, high intensity laser facilities are approaching the 10 Hz shot rate at petawatt powers, but are currently unable to insert targets at these rates. We have developed liquid crystal films to address this need for high rep rate targets while preserving the planar geometry advantageous to many applications. The molecular ordering of liquid crystal is variable with temperature and can be manipulated to form a layered thin film. In this way temperature and volume control can be used to vary film thickness in vacuo and on-demand between 10 nm and over 10 μm. These techniques were previously applied to a single-shot ion acceleration experiment in, where target thickness critically determines the physics of the acceleration. Here we present an automatic film formation device that utilizes a linear sliding rail to form liquid crystal films within the aforementioned range at rates up to 0.1 Hz. The design ensures film formation location within 2 μm RMS, well within the Rayleigh range of even short f-number systems. Details of liquid crystal films and this target formation device will be shown as well as recent experimental data from the Scarlet laser facility at OSU. This work was supported by DARPA through a grant from AMRDEC.

Fast repetition rate (FRR) fluorometer and method for measuring fluorescence and photosynthetic parameters

DOEpatents

Kolber, Z.; Falkowski, P.

1995-06-20

A fast repetition rate fluorometer device and method for measuring in vivo fluorescence of phytoplankton or higher plants chlorophyll and photosynthetic parameters of phytoplankton or higher plants is revealed. The phytoplankton or higher plants are illuminated with a series of fast repetition rate excitation flashes effective to bring about and measure resultant changes in fluorescence yield of their Photosystem II. The series of fast repetition rate excitation flashes has a predetermined energy per flash and a rate greater than 10,000 Hz. Also, disclosed is a flasher circuit for producing the series of fast repetition rate flashes. 14 figs.

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.

Material variability and repetitive member factors for the allowable properties of engineered wood products

Treesearch

Steve Verrill; David E. Kretschmann

2009-01-01

It has been argued that repetitive member allowable property adjustments should be larger for high-variability materials than for low-variability materials. We report analytic calculations and simulations that suggest that the order of such adjustments should be reversed, that is, given the manner in which allowable properties are currently calculated, as the...

Material variability and repetitive member allowable property adjustments in forest products engineering

Treesearch

Steve Verrill; David Kretschmann

2008-01-01

It has been argued that repetitive member allowable property adjustments should be larger for high-variability material than for low-variability material. We report analytic calculations and simulations that suggest that the order of such adjustments should be reversed. That is, given the manner in which allowable properties are currently calculated, as the coefficient...

Intratypic variability of a tandem repeat locus within the DNA polymerase gene of human herpes simplex virus type 2.

PubMed

Sun, Yongjiang; Chan, Roy Kum Wah; Tan, Suat Hoon

2004-01-01

In this study, the irntratypic variability of a tandem repeat locus within the DNA polymerase (pol) gene of human herpes simplex virus type 2 (HSV2) was uncovered. The locus contained variable numbers of tandem dodecanucleotide (5'-GAC GAG GAC GGG-3') repetitive units. Our result showed that approximately 95% of analyzed HSV2 clinical isolates and the current GenBank HSV2 strains contained two copies of the repetitive units. From genital herpes specimens, three new HSV2 strains, which respectively contained 1, 3, and 4 copies of the repetitive units, were identified. This variable number of tandem repeat (VNTR) locus is absent in HSV1, and thus it also contributes to the intertypic variability of HSV1 and HSV2. The intratypic variability of the locus may be useful for HSV2 strain genotyping and this application is discussed.

How Do Algebra I Course Repetition Rates Vary among English Learner Students by Length of Time to Reclassification as English Proficient? REL 2017-222

ERIC Educational Resources Information Center

Jaquet, Karina; Fong, Anthony B.

2017-01-01

Research has found high repetition rates for students in Algebra I, with one study finding a repetition rate of 44 percent for students in a large urban high school district. Less is known about how math performance and Algebra I course repetition rates vary among students with different levels of English proficiency. This report examines Algebra…

Pulse-burst laser systems for fast Thomson scattering (invited)

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

Den Hartog, D. J.; Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706; Ambuel, J. R.

2010-10-15

Two standard commercial flashlamp-pumped Nd:YAG (YAG denotes yttrium aluminum garnet) lasers have been upgraded to ''pulse-burst'' capability. Each laser produces a burst of up to 15 2 J Q-switched pulses (1064 nm) at repetition rates of 1-12.5 kHz. Variable pulse-width drive (0.15-0.39 ms) of the flashlamps is accomplished by insulated gate bipolar transistor (IGBT) switching of electrolytic capacitor banks. Direct control of the laser Pockels cell drive enables optimal pulse energy extraction, and up to four 2 J laser pulses during one flashlamp pulse. These lasers are used in the Thomson scattering plasma diagnostic system on the MST reversed-field pinchmore » to record the dynamic evolution of the electron temperature profile and temperature fluctuations. To further these investigations, a custom pulse-burst laser system with a maximum pulse repetition rate of 250 kHz is now being commissioned.« less

Physiological, Biomechanical, and Medical Aspects of Lifting and Repetitive Lifting: A Review

DTIC Science & Technology

1983-11-01

charateristics of the object lifted. Four major variables have been investigated: 1) box length or dimension of the box in the transverse plane, 2) box...The Department of Labour of Great Britian found that accident rates due to lifting, carrying, pushing and pulling in 1940 was 7.9 per 1000 persons ...employed (25% of the total injuries). In 1956 rates were 6.3 per 1000 persons or 27.7% of the total injuries. In England in 1962 "manual handling

Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance

PubMed Central

Wirth, Klaus; Hartmann, Hagen; Sander, Andre; Mickel, Christoph

2016-01-01

Abstract The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance. PMID:28149424

Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance.

PubMed

Wirth, Klaus; Keiner, Michael; Hartmann, Hagen; Sander, Andre; Mickel, Christoph

2016-12-01

The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance.

Sex differences in kinematic adaptations to muscle fatigue induced by repetitive upper limb movements.

PubMed

Bouffard, Jason; Yang, Chen; Begon, Mickael; Côté, Julie

2018-04-19

Muscle fatigue induced by repetitive movements contributes to the development of musculoskeletal disorders. Men and women respond differently to muscle fatigue during isometric single-joint efforts, but sex differences during dynamic multi-joint tasks have not been clearly identified. Moreover, most studies comparing men and women during fatigue development assessed endurance time. However, none evaluated sex differences in kinematic adaptations to fatigue during multi-joint dynamic tasks. The objective of the study was to compare how men and women adapt their upper body kinematics during a fatiguing repetitive pointing task. Forty men and 41 women performed repetitive pointing movements (one per second) between two targets while maintaining their elbow elevated at shoulder height. The task ended when participants rated a perceived level of fatigue of 8/10. Trunk, humerothoracic, and elbow angles were compared between the first and last 30 s of the experiment and between men and women. Linear positions of the index finger (distance from the target) and the elbow (arm elevation) as well as movement timing were documented as task performance measures. Men (7.4 ± 3.2 min) and women (8.3 ± 4.5 min) performed the repetitive pointing task for a similar duration. For both sex groups, trunk range of motion increased with fatigue while shoulder's and elbow's decreased. Moreover, participants modified their trunk posture to compensate for the decreased humerothoracic elevation. Movements at all joints also became more variable with fatigue. However, of the 24 joint angle variables assessed, only two Sex × Fatigue interactions were observed. Although average humerothoracic elevation angle decreased in both subgroups, this decrease was greater in men (standardized response mean [SRM] - 1.63) than in women (SRM - 1.44). Moreover, the movement-to-movement variability of humerothoracic elevation angle increased only in women (SRM 0.42). Despite many similarities between men's and women's response to fatigue induced by repetitive pointing movements, some sex differences were observed. Those subtle differences may indicate that men's shoulder muscles were more fatigued than women's despite a similar level of perceived exertion. They may also indicate that men and women do not adapt the exact same way to a similar fatigue.

Method for generating high-energy and high repetition rate laser pulses from CW amplifiers

DOEpatents

Zhang, Shukui

2013-06-18

A method for obtaining high-energy, high repetition rate laser pulses simultaneously using continuous wave (CW) amplifiers is described. The method provides for generating micro-joule level energy in pico-second laser pulses at Mega-hertz repetition rates.

Laser heating and ablation at high repetition rate in thermal confinement regime

NASA Astrophysics Data System (ADS)

Brygo, François; Semerok, A.; Oltra, R.; Weulersse, J.-M.; Fomichev, S.

2006-09-01

Laser heating and ablation of materials with low absorption and thermal conductivity (paint and cement) were under experimental and theoretical investigations. The experiments were made with a high repetition rate Q-switched Nd:YAG laser (10 kHz, 90 ns pulse duration and λ = 532 nm). High repetition rate laser heating resulted in pulse per pulse heat accumulation. A theoretical model of laser heating was developed and demonstrated a good agreement between the experimental temperatures measured with the infrared pyrometer and the calculated ones. With the fixed wavelength and laser pulse duration, the ablation threshold fluence of paint was found to depend on the repetition rate and the number of applied pulses. With a high repetition rate, the threshold fluence decreased significantly when the number of applied pulses was increasing. The experimentally obtained thresholds were well described by the developed theoretical model. Some specific features of paint heating and ablation with high repetition rate lasers are discussed.

Nonword repetition and nonword reading abilities in adults who do and do not stutter.

PubMed

Sasisekaran, Jayanthi

2013-09-01

In the present study a nonword repetition and a nonword reading task were used to investigate the behavioral (speech accuracy) and speech kinematic (movement variability measured as lip aperture variability index; speech duration) profiles of groups of young adults who do (AWS) and do not stutter (control). Participants were 9 AWS (8 males, Mean age=32.2, SD=14.7) and 9 age- and sex-matched control participants (Mean age=31.8, SD=14.6). For the nonword repetition task, participants were administered the Nonword Repetition Test (Dollaghan & Campbell, 1998). For the reading task, participants were required to read out target nonwords varying in length (6 vs. 11 syllables). Repeated measures analyses of variance were conducted to compare the groups in percent speech accuracy for both tasks; only for the nonword reading task, the groups were compared in movement variability and speech duration. The groups were comparable in percent accuracy in nonword repetition. Findings from nonword reading revealed a trend for the AWS to show a lower percent of accurate productions compared to the control group. AWS also showed significantly higher movement variability and longer speech durations compared to the control group in nonword reading. Some preliminary evidence for group differences in practice effect (seen as differences between the early vs. later 5 trials) was evident in speech duration. Findings suggest differences between AWS and control groups in phonemic encoding and/or speech motor planning and production. Findings from nonword repetition vs. reading highlight the need for careful consideration of nonword properties. At the end of this activity the reader will be able to: (a) summarize the literature on nonword repetition skills in adults who stutter, (b) describe processes underlying nonword repetition and nonword reading, (c) summarize whether or not adults who stutter differ from those who do not in the behavioral and kinematic markers of nonword reading performance, (d) discuss future directions for research. Copyright © 2013 Elsevier Inc. All rights reserved.

Consonant Age-of-Acquisition Effects in Nonword Repetition Are Not Articulatory in Nature

ERIC Educational Resources Information Center

Moore, Michelle W.; Fiez, Julie A.; Tompkins, Connie A.

2017-01-01

Purpose: Most research examining long-term-memory effects on nonword repetition (NWR) has focused on lexical-level variables. Phoneme-level variables have received little attention, although there are reasons to expect significant sublexical effects in NWR. To further understand the underlying processes of NWR, this study examined effects of…

Service provision and outcome for deliberate self-poisoning in adults--results from a six centre descriptive study.

PubMed

Kapur, Navneet; House, Allan; May, Chris; Creed, Francis

2003-07-01

The aim of the study was to compare the hospital management and direct costs of self-poisoning in six United Kingdom hospitals and to investigate whether hospital management influences outcome. This was a prospective descriptive study carried out at three teaching hospitals and three district general hospitals in North West England on adults (aged 16 or over) presenting to the study centres with deliberate self-poisoning over a 5-month period. Data were based on demographic and clinical characteristics, management of the current episode, direct costs and repetition of self-poisoning within 12 weeks of index episode. There were 1778 episodes of self-poisoning during the study period. There were marked differences in management between centres. There was a fivefold difference in the rate of admission to a medical bed (16.5%-81.3%), and a twofold difference in the rate of psychosocial assessment (28.5%-57.7%). These differences remained after adjustment for demographic and clinical factors. Hospital costs per episode varied from pound 228 to pound 422 and repetition rate ranged from 10% to 16%. Psychosocial assessment was associated with a twofold reduction in the risk of repetition. The marked variability of services for self-poisoning continue. It seems likely that this is having a detrimental effect on patient outcomes. Large scale intervention studies are required to inform both clinical practice and service provision.

Contact heat-evoked temporal summation: tonic versus repetitive-phasic stimulation.

PubMed

Granot, Michal; Granovsky, Yelena; Sprecher, Elliot; Nir, Rony-Reuven; Yarnitsky, David

2006-06-01

Temporal summation (TS) is usually evoked by repetitive mechanical or electrical stimuli, and less commonly by tonic heat pain. The present study aimed to examine the TS induction by repetitive-phasic versus tonic heat pain stimuli. Using 27 normal volunteers, we compared the extent of summation by three calculation methods: start-to-end pain rating difference, percent change, and double-logarithmic regression of successive ratings along the stimulation. Subjects were tested twice, and the reliability of each of the paradigms was obtained. In addition, personality factors related to pain catastrophizing and anxiety level were also correlated with the psychophysical results. Both paradigms induced significant TS, with similar increases for the repetitive-phasic and the tonic paradigms, as measured on 0-100 numerical pain scale (from 52.9+/-11.7 to 80.2+/-15.5, p<0.001; and from 38.5+/-13.3 to 75.8+/-18.3, p<0.001, respectively). The extent of summation was significantly correlated between the two paradigms, when calculated by absolute change (r=0.543, p=0.004) and by regression (r=0.438, p=0.025). Session-to-session variability was similar for both paradigms, relatively large, yet not biased. As with other psychophysical parameters, this poses some limitations on TS assessment in individual patients over time. The extent of TS induced by both paradigms was found to be associated with anxiety level and pain catastrophizing. Despite some dissimilarity between the repetitive-phasic and the tonic paradigms, the many similarities suggest that the two represent a similar physiological process, even if not precisely the same. Future clinical applications of these tests will determine the clinical relevance of the TS paradigms presented in this study.

Long-Term Cognitive and Neuropsychiatric Consequences of Repetitive Concussion and Head-Impact Exposure.

PubMed

McAllister, Thomas; McCrea, Michael

2017-03-01

Initially, interest in sport-related concussion arose from the premise that the study of athletes engaged in sports associated with high rates of concussion could provide insight into the mechanisms, phenomenology, and recovery from mild traumatic brain injury. Over the last decade, concerns have focused on the possibility that, for some athletes, repetitive concussions may raise the long-term risk for cognitive decline, neurobehavioral changes, and neurodegenerative disease. First conceptualized as a discrete event with variable recovery trajectories, concussion is now viewed by some as a trigger of neurobiological events that may influence neurobehavioral function over the course of the life span. Furthermore, advances in technology now permit us to gain a detailed understanding of the frequency and intensity of repetitive head impacts associated with contact sports (eg, football, ice hockey). Helmet-based sensors can be used to characterize the kinematic features of concussive impacts, as well as the profiles of typical head-impact exposures experienced by athletes in routine sport participation. Many large-magnitude impacts are not associated with diagnosed concussions, whereas many diagnosed concussions are associated with more modest impacts. Therefore, a full understanding of this topic requires attention to not only the effects of repetitive concussions but also overall exposure to repetitive head impacts. This article is a review of the current state of the science on the long-term neurocognitive and neurobehavioral effects of repetitive concussion and head-impact exposure in contact sports.

Long-Term Cognitive and Neuropsychiatric Consequences of Repetitive Concussion and Head-Impact Exposure

PubMed Central

McAllister, Thomas; McCrea, Michael

2017-01-01

Initially, interest in sport-related concussion arose from the premise that the study of athletes engaged in sports associated with high rates of concussion could provide insight into the mechanisms, phenomenology, and recovery from mild traumatic brain injury. Over the last decade, concerns have focused on the possibility that, for some athletes, repetitive concussions may raise the long-term risk for cognitive decline, neurobehavioral changes, and neurodegenerative disease. First conceptualized as a discrete event with variable recovery trajectories, concussion is now viewed by some as a trigger of neurobiological events that may influence neurobehavioral function over the course of the life span. Furthermore, advances in technology now permit us to gain a detailed understanding of the frequency and intensity of repetitive head impacts associated with contact sports (eg, football, ice hockey). Helmet-based sensors can be used to characterize the kinematic features of concussive impacts, as well as the profiles of typical head-impact exposures experienced by athletes in routine sport participation. Many large-magnitude impacts are not associated with diagnosed concussions, whereas many diagnosed concussions are associated with more modest impacts. Therefore, a full understanding of this topic requires attention to not only the effects of repetitive concussions but also overall exposure to repetitive head impacts. This article is a review of the current state of the science on the long-term neurocognitive and neurobehavioral effects of repetitive concussion and head-impact exposure in contact sports. PMID:28387556

Variable training does not lead to better motor learning compared to repetitive training in children with and without DCD when exposed to active video games.

PubMed

Bonney, Emmanuel; Jelsma, Dorothee; Ferguson, Gillian; Smits-Engelsman, Bouwien

2017-03-01

Little is known about the influence of practice schedules on motor learning and skills transfer in children with and without developmental coordination disorder (DCD). Understanding how practice schedules affect motor learning is necessary for motor skills development and rehabilitation. The study investigated whether active video games (exergames) training delivered under variable practice led to better learning and transfer than repetitive practice. 111 children aged 6-10 years (M=8.0, SD=1.0) with no active exergaming experience were randomized to receive exergames training delivered under variable (Variable Game Group (VGG), n=56) or repetitive practice schedule (Repetitive Game Group (RGG), n=55). Half the participants were identified as DCD using the DSM-5 criteria, while the rest were typically developing (TD), age-matched children. Both groups participated in two 20min sessions per week for 5 weeks. Both participant groups (TD and DCD) improved equally well on game performance. There was no significant difference in positive transfer to balance tasks between practice schedules (Repetitive and Variable) and participant groups (TD and DCD). Children with and without DCD learn balance skills quite well when exposed to exergames. Gains in learning and transfer are similar regardless of the form of practice schedule employed. This is the first paper to compare the effect of practice schedules on learning in children with DCD and those with typical development. No differences in motor learning were found between repetitive and variable practice schedules. When children with and without DCD spend the same amount of time on exergames, they do not show any differences in acquisition of motor skills. Transfer of motor skills is similar in children with and without DCD regardless of differences in practice schedules. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sensitivity to envelope-based interaural delays at high frequencies: center frequency affects the envelope rate-limitation.

PubMed

Bernstein, Leslie R; Trahiotis, Constantine

2014-02-01

Sensitivity to ongoing interaural temporal disparities (ITDs) was measured using bandpass-filtered pulse trains centered at 4600, 6500, or 9200 Hz. Save for minor differences in the exact center frequencies, those target stimuli were those employed by Majdak and Laback [J. Acoust. Soc. Am. 125, 3903-3913 (2009)]. At each center frequency, threshold ITD was measured for pulse repetition rates ranging from 64 to 609 Hz. The results and quantitative predictions by a cross-correlation-based model indicated that (1) at most pulse repetition rates, threshold ITD increased with center frequency, (2) the cutoff frequency of the putative envelope low-pass filter that determines sensitivity to ITD at high envelope rates appears to be inversely related to center frequency, and (3) both outcomes were accounted for by assuming that, independent of the center frequency, the listeners' decision variable was a constant criterion change in interaural correlation of the stimuli as processed internally. The finding of an inverse relation between center frequency and the envelope rate limitation, while consistent with much prior literature, runs counter to the conclusion reached by Majdak and Laback.

Quantitative measuring system for combustible gas with audible tick rate

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

Batz, J.E.

1979-09-04

Northern Illinois Gas Co.'s new gas-detection instrument is lightweight, portable, easy to use, and in compliance with industry standards as an intrinsically safe device. The instrument uses a semiconductor gas-sensor element energyzed with the regulated voltage source. Placed in the atmosphere to be tested, the detector generates a signal representative of the concentration of natural gas in the air. A meter displays the signal to determine whether the area is hazardous; a variable-repetition-rate blocking oscillator feeding a speaker responds to the signal, generating an audible tick rate useful in locating a leak.

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

Scattering-type scanning near-field optical microscopy with low-repetition-rate pulsed light source through phase-domain sampling

PubMed Central

Wang, Haomin; Wang, Le; Xu, Xiaoji G.

2016-01-01

Scattering-type scanning near-field optical microscopy (s-SNOM) allows spectroscopic imaging with spatial resolution below the diffraction limit. With suitable light sources, s-SNOM is instrumental in numerous discoveries at the nanoscale. So far, the light sources have been limited to continuous wave or high-repetition-rate pulsed lasers. Low-repetition-rate pulsed sources cannot be used, due to the limitation of the lock-in detection mechanism that is required for current s-SNOM techniques. Here, we report a near-field signal extraction method that enables low-repetition-rate pulsed light sources. The method correlates scattering signals from pulses with the mechanical phases of the oscillating s-SNOM probe to obtain near-field signal, by-passing the apparent restriction imposed by the Nyquist–Shannon sampling theorem on the repetition rate. The method shall enable s-SNOM with low-repetition-rate pulses with high-peak-powers, such as femtosecond laser amplifiers, to facilitate investigations of strong light–matter interactions and nonlinear processes at the nanoscale. PMID:27748360

Can a model of overlapping gestures account for scanning speech patterns?

PubMed

Tjaden, K

1999-06-01

A simple acoustic model of overlapping, sliding gestures was used to evaluate whether coproduction was reduced for neurologic speakers with scanning speech patterns. F2 onset frequency was used as an acoustic measure of coproduction or gesture overlap. The effects of speaking rate (habitual versus fast) and utterance position (initial versus medial) on F2 frequency, and presumably gesture overlap, were examined. Regression analyses also were used to evaluate the extent to which across-repetition temporal variability in F2 trajectories could be explained as variation in coproduction for consonants and vowels. The lower F2 onset frequencies for disordered speakers suggested that gesture overlap was reduced for neurologic individuals with scanning speech. Speaking rate change did not influence F2 onset frequencies, and presumably gesture overlap, for healthy or disordered speakers. F2 onset frequency differences for utterance-initial and -medial repetitions were interpreted to suggest reduced coproduction for the utterance-initial position. The utterance-position effects on F2 onset frequency, however, likely were complicated by position-related differences in articulatory scaling. The results of the regression analysis indicated that gesture sliding accounts, in part, for temporal variability in F2 trajectories. Taken together, the results of this study provide support for the idea that speech production theory for healthy talkers helps to account for disordered speech production.

Effects of "D"-Amphetamine and Ethanol on Variable and Repetitive Key-Peck Sequences in Pigeons

ERIC Educational Resources Information Center

Ward, Ryan D.; Bailey, Ericka M.; Odum, Amy L.

2006-01-01

This experiment assessed the effects of "d"-Amphetamine and ethanol on reinforced variable and repetitive key-peck sequences in pigeons. Pigeons responded on two keys under a multiple schedule of Repeat and Vary components. In the Repeat component, completion of a target sequence of right, right, left, left resulted in food. In the Vary component,…

Speech task and timing considerations in MRI research

NASA Astrophysics Data System (ADS)

Epstein, Melissa A.; Stone, Maureen

2003-04-01

In order to create dynamic magnetic resonance images, subjects must repeat tokens as much as 30 times in a row, therefore, their precision is critical for image quality. Word repetition rate can be 1 or 1.5 s, and is matched to the rate of image recording. Unlike reciting tokens to the beat of a metronome, subjects must say each token during an extended period of noise that lasts about 75% of the repetition period. Furthermore, some tokens may be more difficult to say repetitively in these conditions. Therefore, this study simulated the acoustics of a MRI recording session to examine the effects of subject, token, and repetition rate on temporal precision. Subjects repeat up to ten mono- to trisyllabic words 30 times each at two repetition rates. Measurements are made of onsets and offsets of one or more phonemes within each word. Preliminary results (five subjects) indicate that there is an effect of subject and word. Further subjects are being measured to corroborate these results and to determine if one repetition rate is better than another and to test subject reliability.

Increasing Learning from TV News.

ERIC Educational Resources Information Center

Perloff, Richard M.; And Others

1982-01-01

Describes an experiment that manipulated two variables, repetition and pausing for viewer "digestion" of information in a news telecast. Concludes that the use of repetition increased viewers' retention of information, but that pauses did not. (FL)

Exercise order in resistance training.

PubMed

Simão, Roberto; de Salles, Belmiro Freitas; Figueiredo, Tiago; Dias, Ingrid; Willardson, Jeffrey M

2012-03-01

Resistance training (RT) is now an integral component of a well rounded exercise programme. For a correct training prescription, it is of the utmost importance to understand the interaction among training variables, such as the load, volume, rest interval between sets and exercises, frequency of sessions, exercise modality, repetition velocity and, finally, exercise order. Sports medicine research has indicated that exercise order is an important variable that affects both acute responses and chronic adaptations to RT programmes. Therefore, the purpose of this review was to analyse and discuss exercise order with relevance to acute responses (e.g. repetition performance) and also the expression of chronic adaptable characteristics (e.g. maximal strength and hypertrophy). To accomplish this purpose, the Scielo, Science Citation Index, National Library of Medicine, MEDLINE, Scopus, SPORTDiscus™ and CINAHL® databases were accessed to locate previously conducted original scientific investigations. The studies reviewed examined both acute responses and chronic adaptations with exercise order as the experimental variable. Generally, with relevance to acute responses, a key finding was that exercise order affects repetition performance over multiple sets, indicating that the total repetitions, and thus the volume, is greater when an exercise is placed at the beginning of an RT session, regardless of the relative amount of muscle mass involved. The pre-exhaustion method might not be an effective technique to increase the extent of neuromuscular recruitment for larger muscle groups (e.g. pectoralis major for the bench press) when preceded by a single-joint movement (e.g. pec-deck fly). With relevance to localized muscular endurance performance, oxygen consumption and ratings of perceived exertion, the limited amount of research conducted thus far indicates that exercise order does not appear to impact the acute expression of these variables. In terms of chronic adaptations, greater strength increases were evident by untrained subjects for the first exercise of a given sequence, while strength increases were inhibited for the last exercise of a given sequence. Additionally, based on strength and hypertrophy (i.e. muscle thickness and volume) effect-size data, the research suggests that exercises be ordered based on priority of importance as dictated by the training goal of a programme, irrespective of whether the exercise involves a relatively large or small muscle group. In summary, exercise order is an important variable that should receive greater attention in RT prescription. When prescribed appropriately with other key prescriptive variables (i.e. load, volume, rest interval between sets and exercises), the exercise order can influence the efficiency, safety and ultimate effectiveness of an RT programme.

Kinetic processes determining attainable pulse repetition rate in pulsed metal vapor lasers

NASA Astrophysics Data System (ADS)

Petrash, Gueorgii G.

1998-06-01

A review of the investigations of the main processes determining the attainable pulse repetition rate of elemental metal vapor pulsed gas discharge self-terminating lasers, such as copper vapor laser, gold vapor laser, lead vapor laser, is given. Kinetic processes during an excitation pulse and interpulse period are considered as well as experiments with lasers operating at high repetition rate.

Development of tolerance of egg plant (Solanum melangena L.) to field application of dimethoate.

PubMed

Khillar, R; Acharya, S; Mohapatra, P K

2010-07-01

Dimethoate, at field concentration (1.419 mg g(-1) fr wt), caused inhibition of photosynthesis, transpiration and stomatal conductance of Solanum melangena L. on first treatment but subsequent treatments caused adaptation and recovery of these parameters. The variable fluorescence (F(v)), dissipation (DI(0)/RC), 2 ms relative variable fluorescence (V(j)), net rate of PS II closure (M(0)), and maximum trapping rate of active PS II (TR(0)/RC) increased initially but reduced to the control value with repetition of treatment. However, fluorescence yield (TR(0)/Abs), electron transport probability (ET(0)/TR(0)) and activity of RC (ET(0)/RC) increased with each treatment. With each subsequent treatment there was enhancement of activities of esterases and decrease of insecticide content of leaves.

Automatic stress-relieving music recommendation system based on photoplethysmography-derived heart rate variability analysis.

PubMed

Shin, Il-Hyung; Cha, Jaepyeong; Cheon, Gyeong Woo; Lee, Choonghee; Lee, Seung Yup; Yoon, Hyung-Jin; Kim, Hee Chan

2014-01-01

This paper presents an automatic stress-relieving music recommendation system (ASMRS) for individual music listeners. The ASMRS uses a portable, wireless photoplethysmography module with a finger-type sensor, and a program that translates heartbeat signals from the sensor to the stress index. The sympathovagal balance index (SVI) was calculated from heart rate variability to assess the user's stress levels while listening to music. Twenty-two healthy volunteers participated in the experiment. The results have shown that the participants' SVI values are highly correlated with their prespecified music preferences. The sensitivity and specificity of the favorable music classification also improved as the number of music repetitions increased to 20 times. Based on the SVI values, the system automatically recommends favorable music lists to relieve stress for individuals.

Very high repetition-rate electro-optical cavity-dumped Nd: YVO4 laser with optics and dynamics stabilities

NASA Astrophysics Data System (ADS)

Liu, Xuesong; Shi, Zhaohui; Huang, Yutao; Fan, Zhongwei; Yu, Jin; Zhang, Jing; Hou, Liqun

2015-02-01

In this paper, a very high repetition-rate, short-pulse, electro-optical cavity-dumped Nd: YVO4 laser is experimentally and theoretically investigated. The laser performance is optimized from two aspects. Firstly, the laser resonator is designed for a good thermal stability under large pump power fluctuation through optics methods. Secondly, dynamics simulation as well as experiments verifies that cavity dumping at very high repetition rate has better stability than medium/high repetition rate. At 30 W, 880 nm pump power, up to 500 kHz, constant 5 ns, stable 1064 nm fundamental-mode laser pulses can be obtained with 10 W average output power.

Passively mode-locked diode-pumped Nd:YVO4 oscillator operating at an ultralow repetition rate.

PubMed

Papadopoulos, D N; Forget, S; Delaigue, M; Druon, F; Balembois, F; Georges, P

2003-10-01

We demonstrate the operation of an ultralow-repetition-rate, high-peak-power, picosecond diode-pumped Nd:YVO4 passively mode-locked laser oscillator. Repetition rates lower than 1 MHz were achieved with the use of a new design for a multiple-pass cavity and a semiconductor saturable absorber. Long-term stable operation at 1.2 MHz with a pulse duration of 16.3 ps and an average output power of 470 mW, corresponding to 24-kW peak-power pulses, is reported. These are to our knowledge the lowest-repetition-rate high-peak-power pulses ever generated directly from apicosecond laser resonator without cavity dumping.

Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

NASA Technical Reports Server (NTRS)

Hallock, Ashley K.; Martin, Adam; Polzin, Kurt; Kimberlin, Adam; Eskridge, Richard

2013-01-01

Fabricated and tested CTP IPPTs at cone angles of 20deg, 38deg, and 60deg, and performed direct single-pulse impulse bit measurements with continuous gas flow. Single pulse performance highest for 38deg angle with impulse bit of approx.1 mN-s for both argon and xenon. Estimated efficiencies low, but not unexpectedly so based on historical data trends and the direction of the force vector in the CTP. Capacitor charging system assembled to provide rapid recharging of capacitor bank, permitting repetition-rate operation. IPPT operated at repetition-rate of 5 Hz, at maximum average power of 2.5 kW, representing to our knowledge the highest average power for a repetitively-pulsed thruster. Average thrust in repetition-rate mode (at 5 kV, 75 sccm argon) was greater than simply multiplying the single-pulse impulse bit and the repetition rate.

Mode-locking evolution in ring fiber lasers with tunable repetition rate.

PubMed

Korobko, D A; Fotiadi, A A; Zolotovskii, I O

2017-09-04

We have applied a simple approach to analyze behavior of the harmonically mode-locked fiber laser incorporating an adjustable Mach-Zehnder interferometer (MZI). Our model is able to describe key features of the laser outputs and explore limitations of physical mechanisms responsible for laser operation at different pulse repetition rates tuned over a whole GHz range. At low repetition rates the laser operates as a harmonically mode-locked soliton laser triggered by a fast saturable absorber. At high repetition rates the laser mode-locking occurs due to dissipative four-wave mixing seeded by MZI and gain spectrum filtering. However, the laser stability in this regime is rather low due to poor mode selectivity provided by MZI that is able to support the desired laser operation just near the lasing threshold. The use of a double MZI instead of a single MZI could improve the laser stability and extends the range of the laser tunability. The model predicts a gap between two repetitive rate ranges where pulse train generation is not supported.

Hemispheric Asymmetries in Repetition Enhancement and Suppression Effects in the Newborn Brain

PubMed Central

Bouchon, Camillia; Nazzi, Thierry; Gervain, Judit

2015-01-01

Background The repeated presentation of stimuli typically attenuates neural responses (repetition suppression) or, less commonly, increases them (repetition enhancement) when stimuli are highly complex, degraded or presented under noisy conditions. In adult functional neuroimaging research, these repetition effects are considered as neural correlates of habituation. The development and respective functional significance of these effects in infancy remain largely unknown. Objective This study investigates repetition effects in newborns using functional near-infrared spectroscopy, and specifically the role of stimulus complexity in evoking a repetition enhancement vs. a repetition suppression response, following up on Gervain et al. (2008). In that study, abstract rule-learning was found at birth in cortical areas specific to speech processing, as evidenced by a left-lateralized repetition enhancement of the hemodynamic response to highly variable speech sequences conforming to a repetition-based ABB artificial grammar, but not to a random ABC grammar. Methods Here, the same paradigm was used to investigate how simpler stimuli (12 different sequences per condition as opposed to 140), and simpler presentation conditions (blocked rather than interleaved) would influence repetition effects at birth. Results Results revealed that the two grammars elicited different dynamics in the two hemispheres. In left fronto-temporal areas, we reproduce the early perceptual discrimination of the two grammars, with ABB giving rise to a greater response at the beginning of the experiment than ABC. In addition, the ABC grammar evoked a repetition enhancement effect over time, whereas a stable response was found for the ABB grammar. Right fronto-temporal areas showed neither initial discrimination, nor change over time to either pattern. Conclusion Taken together with Gervain et al. (2008), this is the first evidence that manipulating methodological factors influences the presence or absence of neural repetition enhancement effects in newborns and stimulus variability appears a particularly important factor. Further, this temporal modulation is restricted to the left hemisphere, confirming its specialization for learning linguistic regularities from birth. PMID:26485434

Hemispheric Asymmetries in Repetition Enhancement and Suppression Effects in the Newborn Brain.

PubMed

Bouchon, Camillia; Nazzi, Thierry; Gervain, Judit

2015-01-01

The repeated presentation of stimuli typically attenuates neural responses (repetition suppression) or, less commonly, increases them (repetition enhancement) when stimuli are highly complex, degraded or presented under noisy conditions. In adult functional neuroimaging research, these repetition effects are considered as neural correlates of habituation. The development and respective functional significance of these effects in infancy remain largely unknown. This study investigates repetition effects in newborns using functional near-infrared spectroscopy, and specifically the role of stimulus complexity in evoking a repetition enhancement vs. a repetition suppression response, following up on Gervain et al. (2008). In that study, abstract rule-learning was found at birth in cortical areas specific to speech processing, as evidenced by a left-lateralized repetition enhancement of the hemodynamic response to highly variable speech sequences conforming to a repetition-based ABB artificial grammar, but not to a random ABC grammar. Here, the same paradigm was used to investigate how simpler stimuli (12 different sequences per condition as opposed to 140), and simpler presentation conditions (blocked rather than interleaved) would influence repetition effects at birth. Results revealed that the two grammars elicited different dynamics in the two hemispheres. In left fronto-temporal areas, we reproduce the early perceptual discrimination of the two grammars, with ABB giving rise to a greater response at the beginning of the experiment than ABC. In addition, the ABC grammar evoked a repetition enhancement effect over time, whereas a stable response was found for the ABB grammar. Right fronto-temporal areas showed neither initial discrimination, nor change over time to either pattern. Taken together with Gervain et al. (2008), this is the first evidence that manipulating methodological factors influences the presence or absence of neural repetition enhancement effects in newborns and stimulus variability appears a particularly important factor. Further, this temporal modulation is restricted to the left hemisphere, confirming its specialization for learning linguistic regularities from birth.

Safety and efficacy of low fluence, high repetition rate versus high fluence, low repetition rate 810-nm diode laser for axillary hair removal in Chinese women.

PubMed

Li, Wenhai; Liu, Chengyi; Chen, Zhou; Cai, Lin; Zhou, Cheng; Xu, Qianxi; Li, Houmin; Zhang, Jianzhong

2016-11-01

High-fluence diode lasers with contact cooling have emerged as the gold standard to remove unwanted hair. Lowering the energy should result in less pain and could theoretically affect the efficacy of the therapy. To compare the safety and efficacy of a low fluence high repetition rate 810-nm diode laser to those of a high fluence, low repetition rate diode laser for permanent axillary hair removal in Chinese women. Ninety-two Chinese women received four axillae laser hair removal treatments at 4-week intervals using the low fluence, high repetition rate 810-nm diode laser in super hair removal (SHR) mode on one side and the high fluence, low repetition rate diode laser in hair removal (HR) mode on the other side. Hair counts were done at each follow-up visit and 6-month follow-up after the final laser treatment using a "Hi Quality Hair Analysis Program System"; the immediate pain score after each treatment session was recorded by a visual analog scale. The overall median reduction of hair was 90.2% with the 810-nm diode laser in SHR mode and 87% with the same laser in HR mode at 6-month follow-up. The median pain scores in SHR mode and in HR mode were 2.75 and 6.75, respectively. Low fluence, high repetition rate diode laser can efficiently remove unwanted hair but also significantly improve tolerability and reduce adverse events during the course of treatment.

Influence of pulse repetition rate on percussion drilling of Ti-based alloy by picosecond laser pulses

NASA Astrophysics Data System (ADS)

Kononenko, Taras V.; Freitag, Christian; Sovyk, Dmitry N.; Lukhter, Alexander B.; Skvortsov, Konstantin V.; Konov, Vitaly I.

2018-04-01

Percussion drilling of a Ti-based alloy with 8 ps laser pulses was investigated with emphasis on the influence of the pulse repetition rate (1-300 kHz) on the drilling process. Heat accumulation is found to be responsible for simultaneous significant rise of the average drilling rate, the occurrence of a rim around the hole entrance, as well as noticeable surface oxidation. This can be observed as soon as the repetition rate exceeds a certain critical value, which depends on the pulse energy applied. Dramatic rise of the recast layer thickness inside the growing hole was revealed for the limited range of the repetition rates around the lower boundary of the heat accumulation regime. Possible origins of this phenomenon are discussed.

Time stretch dispersive Fourier transform based single-shot pulse-by-pulse spectrum measurement using a pulse-repetition-frequency-variable gain-switched laser

NASA Astrophysics Data System (ADS)

Furukawa, Hideaki; Makino, Takeshi; Wang, Xiaomin; Kobayashi, Tetsuya; Asghari, Mohammad H.; Trinh, Paul; Jalali, Bahram; Man, Wai Sing; Tsang, Kwong Shing; Wada, Naoya

2018-02-01

The time stretch dispersive Fourier Transform (TS-DFT) technique based on a fiber chromatic dispersion is a powerful tool for pulse-by-pulse single-shot spectrum measurement for highrepetition rate optical pulses. The distributed feedback laser diode (DFB-LD) with the gain switch operation can flexibly change the pulse repetition frequency (PRF). In this paper, we newly introduce a semiconductor gain-switched DFB-LD operating from 1 MHz up to 1 GHz PRF into the TS-DFT based spectrum measurement system to improve the flexibility and the operability. The pulse width can be below 2 ps with a pulse compression technique. We successfully measure the spectrum of each optical pulse at 1 GHz, 100 MHz, and 10 MHz PRF, and demonstrate the flexibility of the measurement system.

High repetition-rate Q-switched and intracavity doubled diode-pumped Nd:YAG laser

NASA Technical Reports Server (NTRS)

Hemmati, Hamid; Lesh, James R.

1992-01-01

A Nd:YAG laser was end pumped with 2.2 W of continuous-wave (CW) diode laser output. Efficient operation of the laser at high repetition rates was emphasized. This laser provides 890 mW of TEM00 CW output at 1064 nm, and 340 mW of 532 nm average power at a Q-switched repetition rate of 25 kHz. Experimental data are compared with analysis.

Development of picosecond time-resolved X-ray absorption spectroscopy by high-repetition-rate laser pump/X-ray probe at Beijing Synchrotron Radiation Facility.

PubMed

Wang, Hao; Yu, Can; Wei, Xu; Gao, Zhenhua; Xu, Guang Lei; Sun, Da Rui; Li, Zhenjie; Zhou, Yangfan; Li, Qiu Ju; Zhang, Bing Bing; Xu, Jin Qiang; Wang, Lin; Zhang, Yan; Tan, Ying Lei; Tao, Ye

2017-05-01

A new setup and commissioning of transient X-ray absorption spectroscopy are described, based on the high-repetition-rate laser pump/X-ray probe method, at the 1W2B wiggler beamline at the Beijing Synchrotron Radiation Facility. A high-repetition-rate and high-power laser is incorporated into the setup with in-house-built avalanche photodiodes as detectors. A simple acquisition scheme was applied to obtain laser-on and laser-off signals simultaneously. The capability of picosecond transient X-ray absorption spectroscopy measurement was demonstrated for a photo-induced spin-crossover iron complex in 6 mM solution with 155 kHz repetition rate.

RESPONSES OF MALE TROPICAL MOCKINGBIRDS TO VARIATION IN WITHIN-SONG AND BETWEEN-SONG VERSATILITY

PubMed Central

Botero, Carlos A.; Vehrencamp, Sandra L.

2007-01-01

Despite their large vocal repertoires and otherwise highly versatile singing style, male mockingbirds sometimes sing in a highly repetitive fashion. We conducted a playback experiment to determine the possible signal value of different syllable presentation patterns during simulated male intrusions in the Tropical Mockingbird (Mimus gilvus) testing the hypothesis that more repetitive singing represents a stronger threat and generates a stronger aggressive response. Responses were measured in terms of approach and singing behavior and were analyzed using McGregor’s (1992) multivariate method. We also introduce the use of survival analysis for analyzing response variables for which subjects do not perform the behavior in question in at least one of the replicates (known as ‘right-censored variables’ in the statistical literature). As predicted by theory, experimental subjects responded more aggressively to songs composed of a single note than to variable ones. However, versatility at the between-song level had an opposite effect as high song switching rates generated stronger responses than low ones. Given the lack of a statistical interaction between within-song versatility and switching rate, we conclude that these two parameters may serve independent purposes and possibly transmit different information. We discuss the possibility that the signal value of variation in vocal versatility lies in the mediation of territorial conflicts, the attraction of female partners and/or the mediation of conflicts over access to reproductive females. PMID:18509510

Erbium:YAG laser contouring of the nasal dorsum: a preliminary investigation

NASA Astrophysics Data System (ADS)

Truong, Mai T.; Majaron, Boris; Pandoh, Nidhi S.; Wong, Brian J.

2001-05-01

In conventional aesthetic rhinoplasty operations, manual or powered rasps are used to reduce the osseo-cartilagenous nasal dorsum. This tactile method requires palpation of the instrument and the dorsum during surgery to estimate the degree of volume reduction, and often requires forceful manipulation of the dorsum which may illicit pain during surgery and contribute to post-operative edema and echymosis. In this preliminary study, we investigated the use of the Erbium:YAG laser ((lambda) equals294 micrometers ) to reduce bone and cartilage using ex-vivo porcine nasal dorsum and human cadaveric tissues. The short pulsed length and high absorption of this laser in biologic tissues results in minimization of thermal injury which are ideal for non- contact optical contouring of osseous and cartilagenous tissues in the face. Two Erbium:YAG lasers were used to ablate fresh porcine nasal bone and compared for their use. One Erbium:YAG laser, the Fidelis Laser, Fontana Medical Lasers, Ljubljana, Slovenija with variable pulse repetition rates (2 to 50 Hz), pulse energy (80 to 1000 mJ), and pulse duration (100, 300, 750 and 1000 microsecond(s) ) was used and compared to the Ultrafine Erbium:YAG laser, Coherent Inc., Santa Clara California, with variable pulse repetition rate (2 to 10 Hz), pulse energy (2-16 J/cm2), and spot diameter (2-6 mm). Only laser parameters approximating the conditions for thermal confinement were evaluated.

Learning better by repetition or variation? Is transfer at odds with task specific training?

PubMed

Bonney, Emmanuel; Jelsma, Lemke Dorothee; Ferguson, Gillian D; Smits-Engelsman, Bouwien C M

2017-01-01

Transfer of motor skills is the ultimate goal of motor training in rehabilitation practice. In children with Developmental Coordination Disorder (DCD), very little is known about how skills are transferred from training situations to real life contexts. In this study we examined the influence of two types of practice on transfer of motor skills acquired in a virtual reality (VR) environment. One hundred and eleven children with DCD and their typically developing (TD) peers, aged 6-10 years (M = 8.0 SD = 1.0) were randomly assigned to either variable (n = 56) or repetitive practice (n = 55). Participants in the repetitive practice played the same exergame (ski slalom) twice weekly for 20 minutes, over a period of 5 weeks, while those in the variable group played 10 different games. Motor skills such as balance tasks (hopping), running and agility tasks, ball skills and functional activities were evaluated before and after 5 weeks of training. ANOVA repeated measures indicated that both DCD and TD children demonstrated transfer effects to real life skills with identical and non-identical elements at exactly the same rate, irrespective of the type of practice they were assigned to. Based on these findings, we conclude that motor skills acquired in the VR environment, transfers to real world contexts in similar proportions for both TD and DCD children. The type of practice adopted does not seem to influence children's ability to transfer skills acquired in an exergame to life situations but the number of identical elements does.

AC Resonant charger with charge rate unrelated to primary power frequency

DOEpatents

Watson, Harold

1982-01-01

An AC resonant charger for a capacitive load, such as a PFN, is provided with a variable repetition rate unrelated to the frequency of a multi-phase AC power source by using a control unit to select and couple the phase of the power source to the resonant charger in order to charge the capacitive load with a phase that is the next to begin a half cycle. For optimum range in repetition rate and increased charging voltage, the resonant charger includes a step-up transformer and full-wave rectifier. The next phase selected may then be of either polarity, but is always selected to be of a polarity opposite the polarity of the last phase selected so that the transformer core does not saturate. Thyristors are used to select and couple the correct phase just after its zero crossover in response to a sharp pulse generated by a zero-crossover detector. The thyristor that is turned on then automatically turns off after a full half cycle of its associated phase input. A full-wave rectifier couples the secondary winding of the transformer to the load so that the load capacitance is always charged with the same polarity.

Ac resonant charger with charge rate unrelated to preimary power requency

DOEpatents

Not Available

1979-12-07

An ac resonant charger for a capacitive load, such as a pulse forming network (PFN), is provided with a variable repetition rate unrelated to the frequency of a multi-phase ac power source by using a control unit to select and couple the phase of the power source to the resonant charger in order to charge the capacitive load with a phase that is the next to begin a half cycle. For optimum range in repetition rate and increased charging voltage, the resonant charger includes a step-up transformer and full-wave rectifier. The next phase selected may then be of either polarity, but is always selected to be of a polarity opposite the polarity of the last phase selected so that the transformer core does not saturate. Thyristors are used to select and couple the correct phase just after its zero crossover in response to a sharp pulse generated by a zero-crossover detector. The thyristor that is turned on then automatically turns off after a full half cycle of its associated phase input. A full-wave rectifier couples the secondary winding of the transformer to the load so that the load capacitance is always charged with the same polarity.

Meaningful Words and Non-Words Repetitive Articulatory Rate (Oral Diadochokinesis) in Persian Speaking Children

ERIC Educational Resources Information Center

Zamani, Peyman; Rezai, Hossein; Garmatani, Neda Tahmasebi

2017-01-01

Repetitive articulatory rate or Oral Diadochokinesis (oral-DDK) shows a guideline for appraisal and diagnosis of subjects with oral-motor disorder. Traditionally, meaningless words repetition has been utilized in this task and preschool children have challenges with them. Therefore, we aimed to determine some meaningful words in order to test…

NMR Investigation of Chloromethane Complexes of Cryptophane-A and Its Analogue with Butoxy Groups

PubMed Central

2014-01-01

Host–guest complexes between cryptophane-A as host and dichloromethane and chloroform as guests are investigated using 1H and 13C NMR spectroscopy. Moreover, a related cryptophane, with the methoxy groups replaced by butoxy units (cryptophane-But), and its complexes with the same guests were also studied. Variable temperature spectra showed effects of chemical exchange between the free and bound guests, as well as of conformational exchange of the host. The guest exchange was studied quantitatively by exchange spectroscopy or line shape analysis. Extraction of kinetic and thermodynamic parameters led to the characterization of the affinity between guests and hosts. On the other hand, the host exchange was investigated by means of 13C Carr–Purcell–Meiboom–Gill (CPMG) relaxation dispersion which aims at the determination of the transverse relaxation rate R2, the inverse of the transverse relaxation time T2, as a function of the repetition of the π pulses in a CPMG train. The variation of the measured transverse relaxation rate with the repetition rate νCPMG indicated conformational exchange occurring on the microsecond–millisecond time scale. Structural information was obtained through measurements of cross-relaxation rates, both within the host and between the host and the guest protons. The NMR results were supported by DFT calculations. PMID:24472055

Validity and reliability of the Behavior Problems Inventory, the Aberrant Behavior Checklist, and the Repetitive Behavior Scale-Revised among infants and toddlers at risk for intellectual or developmental disabilities: a multi-method assessment approach.

PubMed

Rojahn, Johannes; Schroeder, Stephen R; Mayo-Ortega, Liliana; Oyama-Ganiko, Rosao; LeBlanc, Judith; Marquis, Janet; Berke, Elizabeth

2013-05-01

Reliable and valid assessment of aberrant behaviors is essential in empirically verifying prevention and intervention for individuals with intellectual or developmental disabilities (IDD). Few instruments exist which assess behavior problems in infants. The current longitudinal study examined the performance of three behavior-rating scales for individuals with IDD that have been proven psychometrically sound in older populations: the Aberrant Behavior Checklist (ABC), the Behavior Problems Inventory (BPI-01), and the Repetitive Behavior Scale - Revised (RBS-R). Data were analyzed for 180 between six and 36 months old children at risk for IDD. Internal consistency (Cronbach's α) across the subscales of the three instruments was variable. Test-retest reliability of the three BPI-01 subscales ranged from .68 to .77 for frequency ratings and from .65 to .80 for severity ratings (intraclass correlation coefficients). Using a multitrait-multimethod matrix approach high levels of convergent and discriminant validity across the three instruments was found. As anticipated, there was considerable overlap in the information produced by the three instruments; however, each behavior-rating instrument also contributed unique information. Our findings support using all three scales in conjunction if possible. Copyright © 2013 Elsevier Ltd. All rights reserved.

BEAM DYNAMICS STUDIES OF A HIGH-REPETITION RATE LINAC-DRIVER FOR A 4TH GENERATION LIGHT SOURCE

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

Ventturini, M.; Corlett, J.; Emma, P.

2012-05-18

We present recent progress toward the design of a super-conducting linac driver for a high-repetition rate FEL-based soft x-ray light source. The machine is designed to accept beams generated by the APEX photo-cathode gun operating with MHz-range repetition rate and deliver them to an array of SASE and seeded FEL beamlines. We review the current baseline design and report results of beam dynamics studies.

Repetitively Q-switched Nd:BeL lasers

NASA Technical Reports Server (NTRS)

Degnan, J.; Birnbaum, M.; Deshazer, L. G.

1979-01-01

The thermal and mechanical characteristics which will ultimately limit the performance of Nd:BeL at high average power levels were investigated. The output beam characteristics (pulse width, peak power, beam dimensions and collimation) were determined at high repetition rates for both Nd:BeL and Nd:YAG. The output of Nd:BeL was shown to exceed that of Nd:YAG by a factor of 2.7 at low Q-switched repetition rates (1 Hz). This result follows from the smaller stimulated emission cross section of x-axis Nb:BeL compared to that of NdYAG by the same factor. At high repetition rates (10 Hz) the output of Nd:Bel falls to a level of three-fifths of its low repetition rate value while under similar tests the output of Nd:YAG remains essentially constant. A comparison of the measured values of the elasto-optic coefficients, the dn/dT values and the linear expansion coefficients for BeL and YAG failed to provide an explanation for the performance of BeL; however, thermal lensing was observed in Nd:BeL. Results imply that the output of a high repetition rate Q-switched Nd:BeL laser (high thermal loading) could be dramatically increased by utilization of a resonator design to compensate for the thermal lensing effects.

Laterality of repetitive finger movement performance and clinical features of Parkinson's disease.

PubMed

Stegemöller, Elizabeth; Zaman, Andrew; MacKinnon, Colum D; Tillman, Mark D; Hass, Chris J; Okun, Michael S

2016-10-01

Impairments in acoustically cued repetitive finger movement often emerge at rates near to and above 2Hz in persons with Parkinson's Disease (PD) in which some patients move faster (hastening) and others move slower (bradykinetic). The clinical features impacting this differential performance of repetitive finger movement remain unknown. The purpose of this study was to compare repetitive finger movement performance between the more and less affected side, and the difference in clinical ratings among performance groups. Forty-one participants diagnosed with idiopathic PD completed an acoustically cued repetitive finger movement task while "on" medication. Eighteen participants moved faster, 10 moved slower, and 13 were able to maintain the appropriate rate at rates above 2Hz. Clinical measures of laterality, disease severity, and the UPDRS were obtained. There were no significant differences between the more and less affected sides regardless of performance group. Comparison of disease severity, tremor, and rigidity among performance groups revealed no significant differences. Comparison of posture and postural instability scores revealed that the participants that demonstrated hastening had worse posture and postural instability scores. Consideration of movement rate during the clinical evaluation of repetitive finger movement may provide additional insight into varying disease features in persons with PD. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of Repetition Rate on Femtosecond Laser-Induced Homogenous Microstructures

PubMed Central

Biswas, Sanchari; Karthikeyan, Adya; Kietzig, Anne-Marie

2016-01-01

We report on the effect of repetition rate on the formation and surface texture of the laser induced homogenous microstructures. Different microstructures were micromachined on copper (Cu) and titanium (Ti) using femtosecond pulses at 1 and 10 kHz. We studied the effect of the repetition rate on structure formation by comparing the threshold accumulated pulse (FΣpulse) values and the effect on the surface texture through lacunarity analysis. Machining both metals at low FΣpulse resulted in microstructures with higher lacunarity at 10 kHz compared to 1 kHz. On increasing FΣpulse, the microstructures showed higher lacunarity at 1 kHz. The effect of the repetition rate on the threshold FΣpulse values were, however, considerably different on the two metals. With an increase in repetition rate, we observed a decrease in the threshold FΣpulse on Cu, while on Ti we observed an increase. These differences were successfully allied to the respective material characteristics and the resulting melt dynamics. While machining Ti at 10 kHz, the melt layer induced by one laser pulse persists until the next pulse arrives, acting as a dielectric for the subsequent pulse, thereby increasing FΣpulse. However, on Cu, the melt layer quickly resolidifies and no such dielectric like phase is observed. Our study contributes to the current knowledge on the effect of the repetition rate as an irradiation parameter. PMID:28774143

Implementation of continuous-variable quantum key distribution with discrete modulation

NASA Astrophysics Data System (ADS)

Hirano, Takuya; Ichikawa, Tsubasa; Matsubara, Takuto; Ono, Motoharu; Oguri, Yusuke; Namiki, Ryo; Kasai, Kenta; Matsumoto, Ryutaroh; Tsurumaru, Toyohiro

2017-06-01

We have developed a continuous-variable quantum key distribution (CV-QKD) system that employs discrete quadrature-amplitude modulation and homodyne detection of coherent states of light. We experimentally demonstrated automated secure key generation with a rate of 50 kbps when a quantum channel is a 10 km optical fibre. The CV-QKD system utilises a four-state and post-selection protocol and generates a secure key against the entangling cloner attack. We used a pulsed light source of 1550 nm wavelength with a repetition rate of 10 MHz. A commercially available balanced receiver is used to realise shot-noise-limited pulsed homodyne detection. We used a non-binary LDPC code for error correction (reverse reconciliation) and the Toeplitz matrix multiplication for privacy amplification. A graphical processing unit card is used to accelerate the software-based post-processing.

Are rate of perceived exertion and feelings of pleasure/displeasure modified in elderly women undergoing 8 week of strength training of prescribe intensity?

PubMed Central

Benites, Mariana L.; Alves, Ragami C.; Ferreira, Sandro S.; Follador, Lucio; da Silva, Sergio G.

2016-01-01

[Purpose] The aim of the present study was to verify the rate of perceived exertion and feelings of pleasure/displeasure in elderly women, who did normally perform physical exercises, following eight weeks of strength training in a constant routine. [Subjects and Methods] Eleven sedentary women were subjected to anthropometric assessment. The maximum load (100%) for each used in this study was determined by performing a test to determined the 1RM for each of them according to the protocol of Fatouros et al. and the Feeling Scale and RPE scale were explained to the women. After these initial procedures, the subjects followed a routine for strength training, performing three sets of repetitions at 70% of the one-repetition maximum for each exercise (bench press, leg extension, pulldown, leg curl) without modifying the exercises and their execution order. The frequency of training was three days per week. ANOVA was used to analyze the behavior of the dependent variable, and the post hoc tests were used to identify significant differences. [Results] Strength increased only in the fifth week. The rate of perceived exertion showed a reduction only in the fifth week in the leg extension, pulldown, leg curl. [Conclusion] The percentage of 70% the one-repetition maximum recommended to increase the strength gains and hypertrophy of skeletal muscle does not provide feelings of displeasure when performing proposed exercise. However, it may be possible to modulate this percentage to obtain more pleasant feelings over two months. PMID:27065524

Are rate of perceived exertion and feelings of pleasure/displeasure modified in elderly women undergoing 8 week of strength training of prescribe intensity?

PubMed

Benites, Mariana L; Alves, Ragami C; Ferreira, Sandro S; Follador, Lucio; da Silva, Sergio G

2016-01-01

[Purpose] The aim of the present study was to verify the rate of perceived exertion and feelings of pleasure/displeasure in elderly women, who did normally perform physical exercises, following eight weeks of strength training in a constant routine. [Subjects and Methods] Eleven sedentary women were subjected to anthropometric assessment. The maximum load (100%) for each used in this study was determined by performing a test to determined the 1RM for each of them according to the protocol of Fatouros et al. and the Feeling Scale and RPE scale were explained to the women. After these initial procedures, the subjects followed a routine for strength training, performing three sets of repetitions at 70% of the one-repetition maximum for each exercise (bench press, leg extension, pulldown, leg curl) without modifying the exercises and their execution order. The frequency of training was three days per week. ANOVA was used to analyze the behavior of the dependent variable, and the post hoc tests were used to identify significant differences. [Results] Strength increased only in the fifth week. The rate of perceived exertion showed a reduction only in the fifth week in the leg extension, pulldown, leg curl. [Conclusion] The percentage of 70% the one-repetition maximum recommended to increase the strength gains and hypertrophy of skeletal muscle does not provide feelings of displeasure when performing proposed exercise. However, it may be possible to modulate this percentage to obtain more pleasant feelings over two months.

Design of a High Intensity Turbulent Combustion System

DTIC Science & Technology

2015-05-01

nth repetition of a turbulent-flow experiment. [1] .................... 8 Figure 2. 3: Velocity measurement on the n th repetition of a turbulent-flow...measurement on the n th repetition of a turbulent-flow experiment. u(t) = U + u’(t...event such as P ≈ [ U < N ms-1 ]. The random variable U can be characterized by its probability density function (PDF). The probability of an event

Spectral distortion of dual-comb spectrometry due to repetition rate fluctuation

NASA Astrophysics Data System (ADS)

Hong-Lei, Yang; Hao-Yun, Wei; Yan, Li

2016-04-01

Dual-comb spectrometry suffers the fluctuations of parameters in combs. We demonstrate that the repetition rate is more important than any other parameter, since the fluctuation of the repetition rate leads to a change of difference in the repetition rate between both combs, consequently causing the conversion factor variation and spectral frequency misalignment. The measured frequency noise power spectral density of the repetition rate exhibits an integrated residual frequency modulation of 1.4 Hz from 1 Hz to 100 kHz in our system. This value corresponds to the absorption peak fluctuation within a root mean square value of 0.19 cm-1 that is verified by both simulation and experimental result. Further, we can also simulate spectrum degradation as the fluctuation varies. After modifying misaligned spectra and averaging, the measured result agrees well with the simulated spectrum based on the GEISA database. Project supported by the State Key Laboratory of Precision Measurement Technology & Instruments of Tsinghua University and the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205147).

Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation.

PubMed

Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W; Akens, Margarete K; Lilge, Lothar; Marjoribanks, Robin S

2016-06-01

High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles.

Fiber-based tunable repetition rate source for deep tissue two-photon fluorescence microscopy.

PubMed

Charan, Kriti; Li, Bo; Wang, Mengran; Lin, Charles P; Xu, Chris

2018-05-01

Deep tissue multiphoton imaging requires high peak power to enhance signal and low average power to prevent thermal damage. Both goals can be advantageously achieved through laser repetition rate tuning instead of simply adjusting the average power. We show that the ideal repetition rate for deep two-photon imaging in the mouse brain is between 1 and 10 MHz, and we present a fiber-based source with an arbitrarily tunable repetition rate within this range. The performance of the new source is compared to a mode-locked Ti:Sapphire (Ti:S) laser for in vivo imaging of mouse brain vasculature. At 2.5 MHz, the fiber source requires 5.1 times less average power to obtain the same signal as a standard Ti:S laser operating at 80 MHz.

Experimental investigation of different regimes of mode-locking in a high repetition rate passively mode-locked semiconductor quantum-dot laser.

PubMed

Kéfélian, Fabien; O'Donoghue, Shane; Todaro, Maria Teresa; McInerney, John; Huyet, Guillaume

2009-04-13

We report experimental investigations on a two-section 16-GHz repetition rate InAs/GaAs quantum dot passively mode-locked laser. Near the threshold current, pseudo-periodic Q-switching with complex dynamics is exhibited. Mode-locking operation regimes characterized by different repetition rates and timing jitter levels are encountered up to twice the threshold current. Evolution of the RF spectrum and optical spectrum with current is compared. The different mode-locked regimes are shown to be associated with different spectral and temporal shapes, ranging from 1.3 to 6 ps. This point is discussed by introducing the existence of two different supermodes. Repetition rate evolution and timing jitter increase is attributed to the coupling between the dominant and the secondary supermodes.

Comparison on different repetition rate locking methods in Er-doped fiber laser

NASA Astrophysics Data System (ADS)

Yang, Kangwen; Zhao, Peng; Luo, Jiang; Huang, Kun; Hao, Qiang; Zeng, Heping

2018-05-01

We demonstrate a systematic comparative research on the all-optical, mechanical and opto-mechanical repetition rate control methods in an Er-doped fiber laser. A piece of Yb-doped fiber, a piezoelectric transducer and an electronic polarization controller are simultaneously added in the laser cavity as different cavity length modulators. By measuring the cavity length tuning ranges, the output power fluctuations, the temporal and frequency repetition rate stability, we show that all-optical method introduces the minimal disturbances under current experimental condition.

Demonstration of a high repetition rate capillary discharge waveguide

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

Gonsalves, A. J., E-mail: ajgonsalves@lbl.gov; Pieronek, C.; Daniels, J.

2016-01-21

A hydrogen-filled capillary discharge waveguide operating at kHz repetition rates is presented for parameters relevant to laser plasma acceleration (LPA). The discharge current pulse was optimized for erosion mitigation with laser guiding experiments and MHD simulation. Heat flow simulations and measurements showed modest temperature rise at the capillary wall due to the average heat load at kHz repetition rates with water-cooled capillaries, which is promising for applications of LPAs such as high average power radiation sources.

High repetition rate Petawatt lasers

NASA Astrophysics Data System (ADS)

Roso, Luis

2018-01-01

Petawatt lasers are now available in a number of facilities around the world and are becoming a very useful tool in physics and engineering. Some of such lasers are able -or will be able soon- to fire at high repetition rates (one shot per second or more). Experiments at such repetition rates have certain peculiarities that are to be briefly exposed here, based on the author's experience with the Salamanca VEGA-3 laser. VEGA-3 is a 30 fs PW laser, firing one shot per second.

Vitamin B-12 Deficiency in Children Is Associated with Grade Repetition and School Absenteeism, Independent of Folate, Iron, Zinc, or Vitamin A Status Biomarkers.

PubMed

Duong, Minh-Cam; Mora-Plazas, Mercedes; Marín, Constanza; Villamor, Eduardo

2015-07-01

Micronutrients are essential to neurocognitive development; yet their role in educational outcomes is unclear. We examined the associations of micronutrient status biomarkers with the risk of grade repetition and rates of school absenteeism in a cohort of school children. We recruited 3156 children aged 5-12 y from public schools in Bogota, Colombia. Circulating ferritin, hemoglobin, zinc, vitamin A, and vitamin B-12; erythrocyte folate; and mean corpuscular volume (MCV) were measured in blood samples obtained at the beginning of the year. Absenteeism was recorded weekly during the school year, and grade repetition was determined the next year. Risk ratios for grade repetition and rate ratios for absenteeism were estimated by categories of micronutrient status indicators with use of Poisson regression, adjusting for potential confounders. The risk of grade repetition was 4.9%, and the absenteeism rate was 3.8 d per child-year of observation. Vitamin B-12 deficiency (<148 pmol/L) was associated with an adjusted 2.36-fold greater risk of grade repetition (95% CI: 1.03, 5.41; P = 0.04) compared with plasma concentrations ≥148 pmol/L. Other micronutrients were not related to grade repetition. Vitamin B-12 deficiency was also associated with school absenteeism rates. Compared with children with plasma vitamin B-12 concentrations ≥148 pmol/L, vitamin B-12-deficient children had a 1.89-times higher adjusted rate (95% CI: 1.53, 2.34; P < 0.0001). Anemia was related to a 72% higher rate (95% CI: 48%, 99%; P < 0.0001), whereas every 5-fL difference in MCV was associated with a 7% lower adjusted rate (95% CI: 4%, 10%; P < 0.0001). Vitamin B-12 deficiency was associated with risk of grade repetition and school absenteeism rates in school children from Bogota, Colombia. The effects of correcting vitamin B-12 deficiency on educational outcomes and neurocognitive development of school children need to be determined in intervention studies. © 2015 American Society for Nutrition.

Short-term Recovery Following Resistance Exercise Leading or not to Failure.

PubMed

González-Badillo, J J; Rodríguez-Rosell, D; Sánchez-Medina, L; Ribas, J; López-López, C; Mora-Custodio, R; Yañez-García, J M; Pareja-Blanco, F

2016-04-01

This study analyzed the time course of recovery following 2 resistance exercise protocols differing in level of effort: maximum (to failure) vs. half-maximum number of repetitions per set. 9 males performed 3 sets of 4 vs. 8 repetitions with their 80% 1RM load, 3×4(8) vs. 3×8(8), in the bench press and squat. Several time-points from 24 h pre- to 48 h post-exercise were established to assess the mechanical (countermovement jump height, CMJ; velocity against the 1 m·s(-1) load, V1-load), biochemical (testosterone, cortisol, GH, prolactin, IGF-1, CK) and heart rate variability (HRV) and complexity (HRC) response to exercise. 3×8(8) resulted in greater neuromuscular fatigue (higher reductions in repetition velocity and velocity against V1-load) than 3×4(8). CMJ remained reduced up to 48 h post-exercise following 3×8(8), whereas it was recovered after 6 h for 3×4(8). Significantly greater prolactin and IGF-1 levels were found for 3×8(8) vs. 3×4(8). Significant reductions in HRV and HRC were observed for 3×8(8) vs. 3×4(8) in the immediate recovery. Performing a half-maximum number of repetitions per set resulted in: 1) a stimulus of faster mean repetition velocities; 2) lower impairment of neuromuscular performance and faster recovery; 3) reduced hormonal response and muscle damage; and 4) lower reduction in HRV and HRC following exercise. © Georg Thieme Verlag KG Stuttgart · New York.

Transient suppression of seizures by repetitive transcranial magnetic stimulation in a case of Rasmussen's encephalitis.

PubMed

Rotenberg, Alexander; Depositario-Cabacar, Dewi; Bae, Erica Hyunji; Harini, Chellamani; Pascual-Leone, Alvaro; Takeoka, Masanori

2008-07-01

Repetitive transcranial magnetic stimulation (rTMS) has been applied with variable success to terminate the seizures of epilepsia partialis continua. The rationale for using this technique to suppress ongoing seizures is the capacity of rTMS to interrupt ongoing neuronal activity, and to produce a lasting decrease in cortical excitability with low-frequency (1 Hz) stimulation. We report a case of epilepsia partialis continua in a child with Rasmussen's encephalitis, in whom seizures were transiently suppressed by 1-Hz rTMS delivered in nine daily 30-minute sessions. In this case, total ictal time was significantly reduced during stimulation, but the daily baseline seizure rate remained unchanged. Notably, the detection and quantification of this short-lived improvement were enabled by recording EEG continuously during the rTMS session. Thus, we present this case to illustrate a potential utility of combined continuous EEG recording and rTMS in seizure treatment.

Somali current studied from SEASAT altimetry

NASA Technical Reports Server (NTRS)

Perigaud, C.; Minster, J. F.; Zlotnicki, V.; Balmino, G.

1984-01-01

Mesoscale variability has been obtained for the world ocean from satellite altimetry by using the repetitive tracks data of SEASAT. No significant results were obtained for the Somali current area for two main reasons: the repetitive tracks are too sparse to cover the expected eddy pattern and these data were obtained in late September and early October when the current is strongly decaying. The non-repetitive period of SEASAT offers the possibility to study a dozen of tracks parallel to the eddy axis or crossing it. These are used here to deduce the dynamic topography of the Somali current. Data error reduction and tide and orbit corrections are addressed. A local geoid was built using a collocation inverse method to combine surface gravity data and altimetry: the repetitive tracks show no variability (which confirms that the current is quasi-inexistent at that time) and can be used as data for the local geoid. This should provide a measure of the absolute dynamic topography of the Somali current.

Fiber-based tunable repetition rate source for deep tissue two-photon fluorescence microscopy

PubMed Central

Charan, Kriti; Li, Bo; Wang, Mengran; Lin, Charles P.; Xu, Chris

2018-01-01

Deep tissue multiphoton imaging requires high peak power to enhance signal and low average power to prevent thermal damage. Both goals can be advantageously achieved through laser repetition rate tuning instead of simply adjusting the average power. We show that the ideal repetition rate for deep two-photon imaging in the mouse brain is between 1 and 10 MHz, and we present a fiber-based source with an arbitrarily tunable repetition rate within this range. The performance of the new source is compared to a mode-locked Ti:Sapphire (Ti:S) laser for in vivo imaging of mouse brain vasculature. At 2.5 MHz, the fiber source requires 5.1 times less average power to obtain the same signal as a standard Ti:S laser operating at 80 MHz. PMID:29760989

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.

Investigating MALDI MSI parameters (Part 1) - A systematic survey of the effects of repetition rates up to 20kHz in continuous raster mode.

PubMed

Steven, Rory T; Dexter, Alex; Bunch, Josephine

2016-07-15

Recent developments in laser performance, combined with the desire for increases in detected ion intensity and throughput, have led to the adoption of high repetition-rate diode-pumped solid-state (DPSS) lasers in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI). Previous studies have demonstrated a more complex relationship between detected ion intensity, stage raster speed and laser pulse repetition rate than the simple linear relationship between number of pulses and detected ion intensity that might be expected. Here we report, for the first time, the interrelated influence of varying laser energy, repetition rate and stage raster speed on detected ion intensity. Thin films of PC 34:1 lipid standard and murine brain tissue with CHCA are analysed by continuous stage raster MALDI MSI. Contrary to previous reports, the optimum laser repetition rate is found to be dependent on both laser energy and stage raster speed and is found to be as high as 20kHz under some conditions. The effects of different repetition rates and raster speeds are also found to vary for different ion species within MALDI MSI of tissue and so may be significant when either targeting specific molecules or seeking to minimize bias. A clear dependence on time between laser pulses is also observed indicating the underlying mechanisms may be related to on-plate hysteresis-exhibiting processes such as matrix chemical modification. Copyright © 2016 Elsevier Inc. All rights reserved.

Effects of pulse frequency of input power on the physical and chemical properties of pulsed streamer discharge plasmas in water

NASA Astrophysics Data System (ADS)

Ruma; Lukes, P.; Aoki, N.; Spetlikova, E.; Hosseini, S. H. R.; Sakugawa, T.; Akiyama, H.

2013-03-01

A repetitive pulsed-power modulator, which employs a magnetic pulse compression circuit with a high-speed thyristor switch, was used to study the effects of the pulse repetition rate of input power on the physical and chemical properties of pulsed discharges in water. Positive high-voltage pulses of 20 kV with repetition rates of up to 1 kHz were used to generate a discharge in water using the point-to-plane electrode geometry. By varying the pulse repetition rate, two distinct modes of the discharge plasma were formed in water. The first mode was characterized by the formation of a corona-like discharge propagating through water in the form of streamer channels. The second mode was formed typically above 500 Hz, when the formation of streamer channels in water was suppressed and all plasmas occurred inside a spheroidal aggregate of very fine gas bubbles surrounding the tip of the high-voltage electrode. The production of hydrogen peroxide, degradation of organic dye Acid Orange 7 (AO7) and inactivation of bacteria Escherichia coli by the discharge in water were studied under different discharge plasma modes in dependence on the pulse repetition rate of input power. The efficiency of both chemical and biocidal processes induced by the plasma in water decreased significantly with pulse repetition rates above 500 Hz.

Postural reconfiguration and cycle-to-cycle variability in patients with work-related musculoskeletal disorders compared to healthy controls and in relation to pain emerging during a repetitive movement task.

PubMed

Longo, Alessia; Meulenbroek, Ruud; Haid, Thomas; Federolf, Peter

2018-05-01

Movement variability in sustained repetitive tasks is an important factor in the context of work-related musculoskeletal disorders. While a popular hypothesis suggests that movement variability can prevent overuse injuries, pain evolving during task execution may also cause variability. The aim of the current study was to investigate, first, differences in movement behavior between volunteers with and without work-related pain and, second, the influence of emerging pain on movement variability. Upper-body 3D kinematics were collected as 22 subjects with musculoskeletal disorders and 19 healthy volunteers performed a bimanual repetitive tapping task with a self-chosen and a given rhythm. Three subgroups were formed within the patient group according to the level of pain the participants experienced during the task. Principal component analysis was applied to 30 joint angle coordinates to characterize in a combined analysis the movement variability associated with reconfigurations of the volunteers' postures and the cycle-to-cycle variability that occurred during the execution of the task. Patients with no task-related pain showed lower cycle-to-cycle variability compared to healthy controls. Findings also indicated an increase in movement variability as pain emerged, manifesting both as frequent postural changes and large cycle-to-cycle variability. The findings suggested a relationship between work-related musculoskeletal disorders and movement variability but further investigation is needed on this issue. Additionally, the findings provided clear evidence that pain increased motor variability. Postural reconfigurations and cycle-to-cycle variability should be considered jointly when investigating movement variability and musculoskeletal disorders. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Role of Working Memory Capacity and Interference Resolution Mechanisms in Task Switching

PubMed Central

Pettigrew, Corinne; Martin, Randi C.

2015-01-01

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response-distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response-distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching. PMID:26594895

The role of working memory capacity and interference resolution mechanisms in task switching.

PubMed

Pettigrew, Corinne; Martin, Randi C

2016-12-01

Theories of task switching have emphasized a number of control mechanisms that may support the ability to flexibly switch between tasks. The present study examined the extent to which individual differences in working memory (WM) capacity and two measures of interference resolution, response-distractor inhibition and resistance to proactive interference (PI), account for variability in task switching, including global costs, local costs, and N-2 repetition costs. A total of 102 young and 60 older adults were tested on a battery of tasks. Composite scores were created for WM capacity, response-distractor inhibition, and resistance to PI; shifting was indexed by rate residual scores, which combine response time and accuracy and account for individual differences in processing speed. Composite scores served as predictors of task switching. WM was significantly related to global switch costs. While resistance to PI and WM explained some variance in local costs, these effects did not reach significance. In contrast, none of the control measures explained variance in N-2 repetition costs. Furthermore, age effects were only evident for N-2 repetition costs, with older adults demonstrating larger costs than young adults. Results are discussed within the context of theoretical models of task switching.

Posture-cognitive dual-tasking: A relevant marker of depression-related psychomotor retardation. An illustration of the positive impact of repetitive transcranial magnetic stimulation in patients with major depressive disorder.

PubMed

Deschamps, Thibault; Sauvaget, Anne; Pichot, Anne; Valrivière, Pierre; Maroulidès, Maxime; Bois, Aurore; Bulteau, Samuel; Thomas-Ollivier, Véronique

2016-12-01

This study examined whether postural control variables, particularly the center-of-pressure (COP) velocity-based parameters, could be a relevant hallmark of depression-related psychomotor retardation (PMR). We first aimed at investigating the interplay between the PMR scores and the COP performance in patients with major depressive disorder (MDD), as compared to age-matched healthy controls; secondly, we focused on the impact of a repetitive transcranial magnetic stimulation (rTMS) treatment on depression, PMR scores and postural performance. 16 MDD patients, and a control group of 16 healthy adults, were asked to maintain quiet standing balance during two trials with or without vision, and while backward counting (dual task). All the position and velocity-based COP variables were computed. Before and after the rTMS session (n eligible MDD = 10), we assessed the depression level with the Montgomery-Asberg Depression Rating Scale (MADRS), the PMR scores with the French Retardation Rating Scale for Depression (ERD), and postural performance. Before the treatment, significant positive partial correlations were found between the pre-ERD scores and the velocity-based COP variables, especially in the dual-task conditions (p < 0.05). In contrast, there was no significant correlation between the post-ERD scores and any postural parameter after the treatment. The MADRS and ERD scores showed a significant decrease between before and after the rTMS intervention. For the first time, the findings clearly validated the view that the assessment of postural performance - easy to envisage in clinical settings-constitutes a reliable and objective marker of PMR in MDD patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

Solid-state YVO4/Nd:YVO4/KTP green laser system for the generation of subnanosecond pulses with adjustable kilohertz repetition rate.

PubMed

Zhang, Haijuan; Zhao, Shengzhi; Yang, Kejian; Li, Guiqiu; Li, Dechun; Zhao, Jia; Wang, Yonggang

2013-09-20

A solid-state green laser generating subnanosecond pulses with adjustable kilohertz repetition rate is presented. This pulse laser system is composed of a Q-switched and mode-locked YVO(4)/Nd:YVO(4)/KTP laser simultaneously modulated by an electro-optic (EO) modulator and a central semiconductor saturable absorption mirror. Because the repetition rate of the Q-switched envelope in this laser depends on the modulation frequency of the EO modulator, so long as the pulsewidth of the Q-switched envelope is shorter than the cavity roundtrip transmit time, i.e., the time interval of two neighboring mode-locking pulses, only one mode-locking pulse exists underneath a Q-switched envelope, resulting in the generation of subnanosecond pulses with kilohertz repetition rate. The experimental results show that the pulsewidth of subnanosecond pulses decreases with increasing pump power and the shortest pulse generated at 1 kHz was 450 ps with pulse energy as high as 252 μJ, corresponding to a peak power of 560 kW. In addition, this laser was confirmed to have high stability, and the pulse repetition rate could be freely adjusted from 1 to 4 kHz.

Vibrational sum-frequency generation spectroscopy of lipid bilayers at repetition rates up to 100 kHz

NASA Astrophysics Data System (ADS)

Yesudas, Freeda; Mero, Mark; Kneipp, Janina; Heiner, Zsuzsanna

2018-03-01

Broadband vibrational sum-frequency generation (BB-VSFG) spectroscopy has become a well-established surface analytical tool capable of identifying the orientation and structure of molecular layers. A straightforward way to boost the sensitivity of the technique could be to increase the laser repetition rate beyond that of standard BB-VSFG spectrometers, which rely on Ti:sapphire lasers operating at repetition rates of 1-5 kHz. Nevertheless, possible thermally induced artifacts in the vibrational spectra due to higher laser average powers are unexplored. Here, we discuss laser power induced temperature accumulation effects that distort the BB-VSFG spectra of 1,2-diacyl-sn-glycero-3-phosphocholine at an interface between two transparent phases at repetition rates of 5, 10, 50, and 100 kHz at constant pulse energy. No heat-induced distortions were found in the spectra, suggesting that the increase in the laser repetition rate provides a feasible route to an improved signal-to-noise ratio or shorter data acquisition times in BB-VSFG spectroscopy for thin films on transparent substrates. The results have implications for future BB-VSFG spectrometers pushing the detection limit for molecular layers with low surface coverage.

5 GHz fundamental repetition rate, wavelength tunable, all-fiber passively mode-locked Yb-fiber laser.

PubMed

Cheng, Huihui; Wang, Wenlong; Zhou, Yi; Qiao, Tian; Lin, Wei; Xu, Shanhui; Yang, Zhongmin

2017-10-30

A passively mode-locked Yb 3+ -doped fiber laser with a fundamental repetition rate of 5 GHz and wavelength tunable performance is demonstrated. A piece of heavily Yb 3+ -doped phosphate fiber with a high net gain coefficient of 5.7 dB/cm, in conjunction with a fiber mirror by directly coating the SiO 2 /Ta 2 O 5 dielectric films on a fiber ferrule is exploited for shortening the laser cavity to 2 cm. The mode-locked oscillator has a peak wavelength of 1058.7 nm, pulse duration of 2.6 ps, and the repetition rate signal has a high signal-to-noise ratio of 90 dB. Moreover, the wavelength of the oscillator is found to be continuously tuned from 1056.7 to 1060.9 nm by increasing the temperature of the laser cavity. Simultaneously, the repetition rate correspondingly decreases from 4.945874 to 4.945496 GHz. Furthermore, the long-term stability of the mode-locked operation in the ultrashort laser cavity is realized by exploiting temperature controls. This is, to the best of our knowledge, the highest fundamental pulse repetition rate for 1-μm mode-locked fiber lasers.

A 100J-level nanosecond pulsed DPSSL for pumping high-efficiency, high-repetition rate PW-class lasers

NASA Astrophysics Data System (ADS)

De Vido, M.; Ertel, K.; Mason, P. D.; Banerjee, S.; Phillips, P. J.; Smith, J. M.; Butcher, T. J.; Chekhlov, O.; Divoky, M.; Pilar, J.; Hooker, C.; Shaikh, W.; Lucianetti, A.; Hernandez-Gomez, C.; Mocek, T.; Edwards, C.; Collier, J. L.

2017-02-01

In this paper, we review the development, at the STFC's Central Laser Facility (CLF), of high energy, high repetition rate diode-pumped solid-state laser (DPSSL) systems based on cryogenically-cooled multi-slab ceramic Yb:YAG. Up to date, two systems have been completed, namely the DiPOLE prototype and the DiPOLE100 system. The DiPOLE prototype has demonstrated amplification of nanosecond pulses in excess of 10 J at 10 Hz repetition rate with an opticalto- optical efficiency of 22%. The larger scale DiPOLE100 system, designed to deliver 100J temporally-shaped nanosecond pulses at 10 Hz repetition rate, has been developed at the CLF for the HiLASE project in the Czech Republic. Recent experiments conducted on the DiPOLE100 system demonstrated the energy scalability of the DiPOLE concept to the 100 J pulse energy level. Furthermore, second harmonic generation experiments carried out on the DiPOLE prototype confirmed the suitability of DiPOLE-based systems for pumping high repetition rate PW-class laser systems based on Ti:sapphire or optical parametric chirped pulse amplification (OPCPA) technology.

Optical resolution photoacoustic microscopy using novel high-repetition-rate passively Q-switched microchip and fiber lasers.

PubMed

Shi, Wei; Kerr, Shaun; Utkin, Ilya; Ranasinghesagara, Janaka; Pan, Lei; Godwal, Yogesh; Zemp, Roger J; Fedosejevs, Robert

2010-01-01

Optical-resolution photoacoustic microscopy (OR-PAM) is a novel imaging technology for visualizing optically absorbing superficial structures in vivo with lateral spatial resolution determined by optical focusing rather than acoustic detection. Since scanning of the illumination spot is required, OR-PAM imaging speed is limited by both scanning speed and laser pulse repetition rate. Unfortunately, lasers with high repetition rates and suitable pulse durations and energies are not widely available and can be cost-prohibitive and bulky. We are developing compact, passively Q-switched fiber and microchip laser sources for this application. The properties of these lasers are discussed, and pulse repetition rates up to 100 kHz are demonstrated. OR-PAM imaging was conducted using a previously developed photoacoustic probe, which enabled flexible scanning of the focused output of the lasers. Phantom studies demonstrate the ability to image with lateral spatial resolution of 7±2 μm with the microchip laser system and 15±5 μm with the fiber laser system. We believe that the high pulse repetition rates and the potentially compact and fiber-coupled nature of these lasers will prove important for clinical imaging applications where real-time imaging performance is essential.

Performance improvement of high repetition rate electro-optical cavity-dumped Nd:GdVO4 laser

NASA Astrophysics Data System (ADS)

Yu, X.; Wang, C.; Ma, Y. F.; Chen, F.; Yan, R. P.; Li, X. D.

2012-02-01

We improved the electro-optical cavity-dumped Nd:GdVO4 laser performance at high repetition rates by employing continuous-grown GdVO4/Nd:GdVO4 composite crystal under 879 nm diode-laser pumping. A constant 3.8 ns duration pulsed laser was obtained and the repetition rate could reach up to 100 kHz with a maximum average output power of 13.1 W and a slope efficiency of 56.4%, corresponding to a peak power of 34.4 kW.

High-repetition-rate short-pulse gas discharge.

PubMed

Tulip, J; Seguin, H; Mace, P N

1979-09-01

A high-average-power short-pulse gas discharge is described. This consists of a volume-preionized transverse discharge of the type used in gas lasers driven by a Blumlein energy storage circuit. The Blumlein circuit is fabricated from coaxial cable, is pulse-charged from a high-repetition-rate Marx-bank generator, and is switched by a high-repetition-rate segmented rail gap. The operation of this discharge under conditions typical of rare-gas halide lasers is described. A maximum of 900 pps was obtained, giving a power flow into the discharge of 30 kW.

Learning better by repetition or variation? Is transfer at odds with task specific training?

PubMed Central

Bonney, Emmanuel; Ferguson, Gillian D.; Smits-Engelsman, Bouwien C. M.

2017-01-01

Objective Transfer of motor skills is the ultimate goal of motor training in rehabilitation practice. In children with Developmental Coordination Disorder (DCD), very little is known about how skills are transferred from training situations to real life contexts. In this study we examined the influence of two types of practice on transfer of motor skills acquired in a virtual reality (VR) environment. Method One hundred and eleven children with DCD and their typically developing (TD) peers, aged 6–10 years (M = 8.0 SD = 1.0) were randomly assigned to either variable (n = 56) or repetitive practice (n = 55). Participants in the repetitive practice played the same exergame (ski slalom) twice weekly for 20 minutes, over a period of 5 weeks, while those in the variable group played 10 different games. Motor skills such as balance tasks (hopping), running and agility tasks, ball skills and functional activities were evaluated before and after 5 weeks of training. Results ANOVA repeated measures indicated that both DCD and TD children demonstrated transfer effects to real life skills with identical and non-identical elements at exactly the same rate, irrespective of the type of practice they were assigned to. Conclusion Based on these findings, we conclude that motor skills acquired in the VR environment, transfers to real world contexts in similar proportions for both TD and DCD children. The type of practice adopted does not seem to influence children’s ability to transfer skills acquired in an exergame to life situations but the number of identical elements does. PMID:28333997

Implementation of Time-Resolved Step-Scan Fourier Transform Infrared (FT-IR) Spectroscopy Using a kHz Repetition Rate Pump Laser

PubMed Central

MAGANA, DONNY; PARUL, DZMITRY; DYER, R. BRIAN; SHREVE, ANDREW P.

2011-01-01

Time-resolved step-scan Fourier transform infrared (FT-IR) spectroscopy has been shown to be invaluable for studying excited-state structures and dynamics in both biological and inorganic systems. Despite the established utility of this method, technical challenges continue to limit the data quality and more wide ranging applications. A critical problem has been the low laser repetition rate and interferometer stepping rate (both are typically 10 Hz) used for data acquisition. Here we demonstrate significant improvement in the quality of time-resolved spectra through the use of a kHz repetition rate laser to achieve kHz excitation and data collection rates while stepping the spectrometer at 200 Hz. We have studied the metal-to-ligand charge transfer excited state of Ru(bipyridine)3Cl2 in deuterated acetonitrile to test and optimize high repetition rate data collection. Comparison of different interferometer stepping rates reveals an optimum rate of 200 Hz due to minimization of long-term baseline drift. With the improved collection efficiency and signal-to-noise ratio, better assignments of the MLCT excited-state bands can be made. Using optimized parameters, carbonmonoxy myoglobin in deuterated buffer is also studied by observing the infrared signatures of carbon monoxide photolysis upon excitation of the heme. We conclude from these studies that a substantial increase in performance of ss-FT-IR instrumentation is achieved by coupling commercial infrared benches with kHz repetition rate lasers. PMID:21513597

Single Longitudinal Mode, High Repetition Rate, Q-switched Ho:YLF Laser for Remote Sensing

NASA Technical Reports Server (NTRS)

Bai, Yingxin; Yu, Jirong; Petzar, Paul; Petros, M.; Chen, Songsheng; Trieu, Bo; Lee, Nyung; Singh, U.

2009-01-01

Ho:YLF/LuLiF lasers have specific applications for remote sensing such as wind-speed measurement and carbon dioxide (CO2) concentration measurement in the atmosphere because the operating wavelength (around 2 m) is located in the eye-safe range and can be tuned to the characteristic lines of CO2 absorption and there is strong backward scattering signal from aerosol (Mie scattering). Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of with a repetition rate of 5 Hz and pulse energy of 75 mJ [1]. For highly precise CO2 measurements with coherent detection technique, a laser with high repetition rate is required to averaging out the speckle effect [2]. In addition, laser efficiency is critically important for the air/space borne lidar applications, because of the limited power supply. A diode pumped Ho:Tm:YLF laser is difficult to efficiently operate in high repetition rate due to the large heat loading and up-conversion. However, a Tm:fiber laser pumped Ho:YLF laser with low heat loading can be operated at high repetition rates efficiently [3]. No matter whether wind-speed or carbon dioxide (CO2) concentration measurement is the goal, a Ho:YLF/LuLiF laser as the transmitter should operate in a single longitudinal mode. Injection seeding is a valid technique for a Q-switched laser to obtain single longitudinal mode operation. In this paper, we will report the new results for a single longitudinal mode, high repetition rate, Q-switched Ho:YLF laser. In order to avoid spectral hole burning and make injection seeding easier, a four mirror ring cavity is designed for single longitudinal mode, high repetition rate Q-switched Ho:YLF laser. The ramp-fire technique is chosen for injection seeding.

High-energy, high-repetition-rate picosecond pulses from a quasi-CW diode-pumped Nd:YAG system.

PubMed

Noom, Daniel W E; Witte, Stefan; Morgenweg, Jonas; Altmann, Robert K; Eikema, Kjeld S E

2013-08-15

We report on a high-power quasi-CW pumped Nd:YAG laser system, producing 130 mJ, 64 ps pulses at 1064 nm wavelength with a repetition rate of 300 Hz. Pulses from a Nd:YVO(4) oscillator are first amplified by a regenerative amplifier to the millijoule level and then further amplified in quasi-CW diode-pumped Nd:YAG modules. Pulsed diode pumping enables a high gain at repetition rates of several hundred hertz, while keeping thermal effects manageable. Birefringence compensation and multiple thermal-lensing-compensated relay-imaging stages are used to maintain a top-hat beam profile. After frequency doubling, 75 mJ pulses are obtained at 532 nm. The intensity stability is better than 1.1%, which makes this laser an attractive pump source for a high-repetition-rate optical parametric amplification system.

Design of a low emittance and high repetition rate S-band photoinjector

NASA Astrophysics Data System (ADS)

Han, Jang-Hui

2014-09-01

As an electron beam injector of X-ray free-electron lasers (FELs), photoinjectors have been developed for the past few decades. Such an injector starting with a photocathode RF gun provides high brightness beams and therefore it is being adopted as an injector of X-ray FELs. In this paper we show how to improve photoinjector performance in terms of emittance and repetition rates by means of injector components optimization, especially with the gun. Transverse emittance at the end of an injector is reduced by optimizing the gun design, gun solenoid position, and accelerating section position. The repetition rate of an injector mainly depends on the gun. It is discussed that a repetition rate of 1 kHz at a normal-conducting S-band photoinjector is feasible by adopting a coaxial RF coupler and improving cooling-water channels surrounding the gun.

Habituation and sensitization of aggression in bullfrogs (Rana catesbeiana): testing the dual-process theory of habituation.

PubMed

Bee, M A

2001-09-01

The aggressive response of male bullfrogs (Rana catesbeiana) habituates with repeated broadcasts of acoustic stimuli simulating a new territorial neighbor. The effects of stimulus repetition rate and stimulus intensity on bullfrog aggressive responses were tested in a field experiment designed to test the assumptions of a dual-process theory of habituation. Synthetic advertisement calls were broadcast at 2 repetition rates and 2 intensities in a factorial design. Bullfrogs were more aggressive at the higher stimulus intensity at both repetition rates. Aggressive responses habituated more slowly at the higher stimulus intensity and slower repetition rate compared with other treatments. Several biotic and abiotic factors had small or negligible effects on aggressive responses. Although consistent with the operation of 2 opposing processes, habituation and sensitization, the data provide only partial support for the assumptions of dual-process theory.

Miniaturized two-stack Blumlein pulser with a variable repetition-rate for non-thermal irreversible-electroporation experiments

NASA Astrophysics Data System (ADS)

Min, Sun-Hong; Kwon, Ohjoon; Sattorov, Matlabjon; Baek, In-Keun; Kim, Seontae; Jeong, Jin-Young; Hong, Dongpyo; Park, Seunghyuk; Park, Gun-Sik

2017-01-01

Non-thermal irreversible electroporation (NTIRE) to avoid thermal damage to cells during intense DC ns pulsed electric fields (nsPEFs) is a recent modality for medical applications. This mechanism, related to bioelectrical dynamics of the cell, is linked to the effect of a DC electric field and a threshold effect with an electrically stimulated membrane for the charge distribution in the cell. To create the NTIRE condition, the pulse width of the nsPEF should be shorter than the charging time constant of the membrane related to the cell radius, membrane capacitance, cytoplasm resistivity, and medium resistivity. It is necessary to design and fabricate a very intense nanosecond DC electric field pulser that is capable of producing voltages up to the level of 100 kV/cm with an artificial pulse width (˜ns) with controllable repetition rates. Many devices to generate intense DC nsPEF using various pulse-forming line technologies have been introduced thus far. However, the previous Blumlein pulse-generating devices are clearly inefficient due to the energy loss between the input voltage and the output voltage. An improved two-stage stacked Blumlein pulse-forming line can overcome this limitation and decrease the energy loss from a DC power supply. A metal oxide silicon field-effect transistor switch with a fast rise and fall time would enable a high repetition rate (max. 100 kHz) and good endurance against very high voltages (DC ˜ 30 kV). The load is designed to match the sample for exposure to cell suspensions consisting of a 200 Ω resistor matched with a Blumlein circuit and two electrodes without the characteristic RC time effect of the circuit (capacitance =0.174 pF).

Neural responses in the primary auditory cortex of freely behaving cats while discriminating fast and slow click-trains.

PubMed

Dong, Chao; Qin, Ling; Liu, Yongchun; Zhang, Xinan; Sato, Yu

2011-01-01

Repeated acoustic events are ubiquitous temporal features of natural sounds. To reveal the neural representation of the sound repetition rate, a number of electrophysiological studies have been conducted on various mammals and it has been proposed that both the spike-time and firing rate of primary auditory cortex (A1) neurons encode the repetition rate. However, previous studies rarely examined how the experimental animals perceive the difference in the sound repetition rate, and a caveat to these experiments is that they compared physiological data obtained from animals with psychophysical data obtained from humans. In this study, for the first time, we directly investigated acoustic perception and the underlying neural mechanisms in the same experimental animal by examining spike activities in the A1 of free-moving cats while performing a Go/No-go task to discriminate the click-trains at different repetition rates (12.5-200 Hz). As reported by previous studies on passively listening animals, A1 neurons showed both synchronized and non-synchronized responses to the click-trains. We further found that the neural performance estimated from the precise temporal information of synchronized units was good enough to distinguish all 16.7-200 Hz from the 12.5 Hz repetition rate; however, the cats showed declining behavioral performance with the decrease of the target repetition rate, indicating an increase of difficulty in discriminating two slower click-trains. Such behavioral performance was well explained by the firing rate of some synchronized and non-synchronized units. Trial-by-trial analysis indicated that A1 activity was not affected by the cat's judgment of behavioral response. Our results suggest that the main function of A1 is to effectively represent temporal signals using both spike timing and firing rate, while the cats may read out the rate-coding information to perform the task in this experiment.

Sensory features and repetitive behaviors in children with autism and developmental delays.

PubMed

Boyd, Brian A; Baranek, Grace T; Sideris, John; Poe, Michele D; Watson, Linda R; Patten, Elena; Miller, Heather

2010-04-01

This study combined parent and observational measures to examine the association between aberrant sensory features and restricted, repetitive behaviors in children with autism (N=67) and those with developmental delays (N=42). Confirmatory factor analysis was used to empirically validate three sensory constructs of interest: hyperresponsiveness, hyporesponsiveness, and sensory seeking. Examining the association between the three derived sensory factor scores and scores on the Repetitive Behavior Scales--Revised revealed the co-occurrence of these behaviors in both clinical groups. Specifically, high levels of hyperresponsive behaviors predicted high levels of repetitive behaviors, and the relationship between these variables remained the same controlling for mental age. We primarily found non-significant associations between hyporesponsiveness or sensory seeking and repetitive behaviors, with the exception that sensory seeking was associated with ritualistic/sameness behaviors. These findings suggest that shared neurobiological mechanisms may underlie hyperresponsive sensory symptoms and repetitive behaviors and have implications for diagnostic classification as well as intervention.

Determinants of School Performance Among Quechua Children in the Peruvian Andes

NASA Astrophysics Data System (ADS)

Jacoby, Enrique; Cueto, Santiago; Pollitt, Ernesto

1999-01-01

In the rural Andes of Peru, primary school inefficiency ranks higher than in the rest of the country, with a nearly 50 per cent rate of first grade repetition. In 1993 the investigators administered a battery of four psycho-educational tests to 360 schoolchildren in the fourth and fifth grades at ten primary schools in the Andean region of Huaraz. They also recorded the children's individual characteristics, i.e. family background, nutritional status, and educational attainment, and rated the schools according to educational features such as classroom size, time devoted to learning, and student-teacher ratio. A year later, in 1994, children were re-examined in the schools using the same test battery. All subjects were small for their age, had poor diets, spoke mostly Quechua at home (Spanish in school), lived in a rural environment, and walked considerable distances to school. Regression analyses of the 1993 data indicated that the performance of Quechua children on verbal tests was heavily influenced by family background, while their mathematical competence was related to school experience. On the other hand, improvement in test scores from one year to the next appeared to be strongly related to test performance in 1993 and less clearly to the other recorded variables. Finally, the schools' promotion rates were clearly associated with test scores from the previous year but less clearly with grade repetition rates.

Repetitive transcranial magnetic stimulation for hallucination in schizophrenia spectrum disorders: A meta-analysis.

PubMed

Zhang, Yingli; Liang, Wei; Yang, Shichang; Dai, Ping; Shen, Lijuan; Wang, Changhong

2013-10-05

This study assessed the efficacy and tolerability of repetitive transcranial magnetic stimulation for treatment of auditory hallucination of patients with schizophrenia spectrum disorders. Online literature retrieval was conducted using PubMed, ISI Web of Science, EMBASE, Medline and Cochrane Central Register of Controlled Trials databases from January 1985 to May 2012. Key words were "transcranial magnetic stimulation", "TMS", "repetitive transcranial magnetic stimulation", and "hallucination". Selected studies were randomized controlled trials assessing therapeutic efficacy of repetitive transcranial magnetic stimulation for hallucination in patients with schizophrenia spectrum disorders. Experimental intervention was low-frequency repetitive transcranial magnetic stimulation in left temporoparietal cortex for treatment of auditory hallucination in schizophrenia spectrum disorders. Control groups received sham stimulation. The primary outcome was total scores of Auditory Hallucinations Rating Scale, Auditory Hallucination Subscale of Psychotic Symptom Rating Scale, Positive and Negative Symptom Scale-Auditory Hallucination item, and Hallucination Change Scale. Secondary outcomes included response rate, global mental state, adverse effects and cognitive function. Seventeen studies addressing repetitive transcranial magnetic stimulation for treatment of schizophrenia spectrum disorders were screened, with controls receiving sham stimulation. All data were completely effective, involving 398 patients. Overall mean weighted effect size for repetitive transcranial magnetic stimulation versus sham stimulation was statistically significant (MD = -0.42, 95%CI: -0.64 to -0.20, P = 0.000 2). Patients receiving repetitive transcranial magnetic stimulation responded more frequently than sham stimulation (OR = 2.94, 95%CI: 1.39 to 6.24, P = 0.005). No significant differences were found between active repetitive transcranial magnetic stimulation and sham stimulation for positive or negative symptoms. Compared with sham stimulation, active repetitive transcranial magnetic stimulation had equivocal outcome in cognitive function and commonly caused headache and facial muscle twitching. Repetitive transcranial magnetic stimulation is a safe and effective treatment for auditory hallucination in schizophrenia spectrum disorders.

Repetitive transcranial magnetic stimulation for hallucination in schizophrenia spectrum disorders: A meta-analysis

PubMed Central

Zhang, Yingli; Liang, Wei; Yang, Shichang; Dai, Ping; Shen, Lijuan; Wang, Changhong

2013-01-01

Objective: This study assessed the efficacy and tolerability of repetitive transcranial magnetic stimulation for treatment of auditory hallucination of patients with schizophrenia spectrum disorders. Data Sources: Online literature retrieval was conducted using PubMed, ISI Web of Science, EMBASE, Medline and Cochrane Central Register of Controlled Trials databases from January 1985 to May 2012. Key words were “transcranial magnetic stimulation”, “TMS”, “repetitive transcranial magnetic stimulation”, and “hallucination”. Study Selection: Selected studies were randomized controlled trials assessing therapeutic efficacy of repetitive transcranial magnetic stimulation for hallucination in patients with schizophrenia spectrum disorders. Experimental intervention was low-frequency repetitive transcranial magnetic stimulation in left temporoparietal cortex for treatment of auditory hallucination in schizophrenia spectrum disorders. Control groups received sham stimulation. Main Outcome Measures: The primary outcome was total scores of Auditory Hallucinations Rating Scale, Auditory Hallucination Subscale of Psychotic Symptom Rating Scale, Positive and Negative Symptom Scale-Auditory Hallucination item, and Hallucination Change Scale. Secondary outcomes included response rate, global mental state, adverse effects and cognitive function. Results: Seventeen studies addressing repetitive transcranial magnetic stimulation for treatment of schizophrenia spectrum disorders were screened, with controls receiving sham stimulation. All data were completely effective, involving 398 patients. Overall mean weighted effect size for repetitive transcranial magnetic stimulation versus sham stimulation was statistically significant (MD = –0.42, 95%CI: –0.64 to –0.20, P = 0.000 2). Patients receiving repetitive transcranial magnetic stimulation responded more frequently than sham stimulation (OR = 2.94, 95%CI: 1.39 to 6.24, P = 0.005). No significant differences were found between active repetitive transcranial magnetic stimulation and sham stimulation for positive or negative symptoms. Compared with sham stimulation, active repetitive transcranial magnetic stimulation had equivocal outcome in cognitive function and commonly caused headache and facial muscle twitching. Conclusion: Repetitive transcranial magnetic stimulation is a safe and effective treatment for auditory hallucination in schizophrenia spectrum disorders. PMID:25206578

Cortical activity predicts good variation in human motor output.

PubMed

Babikian, Sarine; Kanso, Eva; Kutch, Jason J

2017-04-01

Human movement patterns have been shown to be particularly variable if many combinations of activity in different muscles all achieve the same task goal (i.e., are goal-equivalent). The nervous system appears to automatically vary its output among goal-equivalent combinations of muscle activity to minimize muscle fatigue or distribute tissue loading, but the neural mechanism of this "good" variation is unknown. Here we use a bimanual finger task, electroencephalography (EEG), and machine learning to determine if cortical signals can predict goal-equivalent variation in finger force output. 18 healthy participants applied left and right index finger forces to repeatedly perform a task that involved matching a total (sum of right and left) finger force. As in previous studies, we observed significantly more variability in goal-equivalent muscle activity across task repetitions compared to variability in muscle activity that would not achieve the goal: participants achieved the task in some repetitions with more right finger force and less left finger force (right > left) and in other repetitions with less right finger force and more left finger force (left > right). We found that EEG signals from the 500 milliseconds (ms) prior to each task repetition could make a significant prediction of which repetitions would have right > left and which would have left > right. We also found that cortical maps of sites contributing to the prediction contain both motor and pre-motor representation in the appropriate hemisphere. Thus, goal-equivalent variation in motor output may be implemented at a cortical level.

History effects in visual search for monsters: search times, choice biases, and liking.

PubMed

Chetverikov, Andrey; Kristjansson, Árni

2015-02-01

Repeating targets and distractors on consecutive visual search trials facilitates search performance, whereas switching targets and distractors harms search. In addition, search repetition leads to biases in free choice tasks, in that previously attended targets are more likely to be chosen than distractors. Another line of research has shown that attended items receive high liking ratings, whereas ignored distractors are rated negatively. Potential relations between the three effects are unclear, however. Here we simultaneously measured repetition benefits and switching costs for search times, choice biases, and liking ratings in color singleton visual search for "monster" shapes. We showed that if expectations from search repetition are violated, targets are liked to be less attended than otherwise. Choice biases were, on the other hand, affected by distractor repetition, but not by target/distractor switches. Target repetition speeded search times but had little influence on choice or liking. Our findings suggest that choice biases reflect distractor inhibition, and liking reflects the conflict associated with attending to previously inhibited stimuli, while speeded search follows both target and distractor repetition. Our results support the newly proposed affective-feedback-of-hypothesis-testing account of cognition, and additionally, shed new light on the priming of visual search.

Cerebral interregional correlations of associative language processing: a positron emission tomography activation study using fluorine-18 fluorodeoxyglucose.

PubMed

Schreckenberger, M; Gouzoulis-Mayfrank, E; Sabri, O; Arning, C; Schulz, G; Tuttass, T; Wagenknecht, G; Kaiser, H J; Sass, H; Buell, U

1998-11-01

Even though there have been numerous positron emission tomography (PET) activation studies on the perfusional and metabolic bases of language processing, little is known about the intracerebral functional network of language and cognitive processes. It was the aim of this study to investigate the cerebral interregional correlations during voluntary word association versus word repetition in healthy subjects to gain insight into the functional connectivity of associative speech processing. Due to individual variability in functional anatomy, the study protocol was designed as an averaged single-subject study. Eight healthy volunteers performed a verbal association task during fluorine-18 fluorodeoxyglucose (18F-FDG) PET scanning. Two different tasks were performed in randomized order: (a) word repetition (after auditory presentation of nouns) as a control condition, and (b) word association (after auditory presentation of nouns) as a specific semantic activation. The regional metabolic rate of glucose (rMRGlu) was calculated after brain regionalization [112 regions of interest on individual 3D flash magnetic resonance imaging (MRI)] and PET/MRI realignment. Statistical analysis was performed for comparison of association and repetition and for calculation of interregional correlation coefficients during both tasks. Compared with word repetition, word association was associated with significant increases in rMRGlu in the left prefrontal cortex, the left frontal operculum (Broca's area) and the left insula, indicating involvement of these areas in associative language processing. Decreased rMRGlu was found in the left posterior cingulum during word association. During word repetition, highly significant negative correlations were found between the left prefrontal cortex, the contralateral cortex areas and the ipsilateral posterior cingulum. These negative correlations were almost completely eliminated during the association task, suggesting a functional decoupling of the strict intercorrelation pattern.

Interaction of repetitively pulsed high energy laser radiation with matter

NASA Astrophysics Data System (ADS)

Hugenschmidt, M.

1986-05-01

Laser target interaction processes and methods of improving the overall energy balance are discussed. This can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed using a pulsed CO2 laser at mean powers up to 2 KW and repetition rates up to 100 Hz. The rates of temperature rise of aluminum for example are increased by more than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements are found for the overall absorptivities, that are increased by more than an order of magnitude.

Development of a Watt-level gamma-ray source based on high-repetition-rate inverse Compton scattering

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

Mihalcea, D.; Murokh, A.; Piot, P.

2017-07-01

A high-brilliance (~10 22 photon s -1 mm -2 mrad -2 /0.1%) gamma-ray source experiment is currently being planned at Fermilab (E γ≃1.1 MeV). The source implements a high-repetition-rate inverse Compton scattering by colliding electron bunches formed in a ~300-MeV superconducting linac with a high-intensity laser pulse. This paper describes the design rationale along with some of technical challenges associated to producing high-repetition-rate collision. The expected performances of the gamma-ray source are also presented.

Injector Beam Dynamics for a High-Repetition Rate 4th-Generation Light Source

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

Papadopoulos, C. F.; Corlett, J.; Emma, P.

2013-05-20

We report on the beam dynamics studies and optimization methods for a high repetition rate (1 MHz) photoinjector based on a VHF normal conducting electron source. The simultaneous goals of beamcompression and reservation of 6-dimensional beam brightness have to be achieved in the injector, in order to accommodate a linac driven FEL light source. For this, a parallel, multiobjective optimization algorithm is used. We discuss the relative merits of different injector design points, as well as the constraints imposed on the beam dynamics by technical considerations such as the high repetition rate.

Multi-gigahertz repetition rate passively modelocked fiber lasers using carbon nanotubes.

PubMed

Martinez, Amos; Yamashita, Shinji

2011-03-28

There is an increasing demand for all-fiber passively mode-locked lasers with pulse repetition rates in the order of gigahertz for their potential applications in fields such as telecommunications and metrology. However, conventional mode-locked fiber lasers typically operate at fundamental repetition rates of only a few megahertz. In this paper, we report all-fiber laser operation with fundamental repetition rates of 4.24 GHz, 9.63 GHz and 19.45 GHz. This is, to date and to the best of our knowledge, the highest fundamental repetition rate reported for an all-fiber laser. The laser operation is based on the passive modelocking of a miniature all-fiber Fabry-Pérot laser (FFPL) by a carbon nanotube (CNT) saturable absorber. The key components for such device are a very high-gain Er:Yb phosphosilicate fiber and a fiber compatible saturable absorber with very small foot print and very low losses. The laser output of the three lasers was close to transform-limited with a pulsewidth of approximately 1 ps and low noise. As a demonstration of potential future applications for this laser, we also demonstrated supercontinuum generation with a longitudinal mode-spacing of 0.08 nm by launching the laser operating at 9.63 GHz into 30 m of a highly nonlinear dispersion shifted fiber.

Generation of plasma X-ray sources via high repetition rate femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Baguckis, Artūras; Plukis, Artūras; Reklaitis, Jonas; Remeikis, Vidmantas; Giniūnas, Linas; Vengris, Mikas

2017-12-01

In this study, we present the development and characterization of Cu plasma X-ray source driven by 20 W average power high repetition rate femtosecond laser in ambient atmosphere environment. The peak Cu- Kα photon flux of 2.3 × 109 photons/s into full solid angle is demonstrated (with a process conversion efficiency of 10-7), using pulses with peak intensity of 4.65 × 1014 W/cm2. Such Cu- Kα flux is significantly larger than others found in comparable experiments, performed in air environment. The effects of resonance plasma absorption process, when optimized, are shown to increase measured flux by the factor of 2-3. The relationship between X-ray photon flux and plasma-driving pulse repetition rate is quasi-linear, suggesting that fluxes could further be increased to 1010 photons/s using even higher average powers of driving radiation. These results suggest that to fully utilize the potential of high repetition rate laser sources, novel target material delivery systems (for example, jet-based ones) are required. On the other hand, this study demonstrates that high energy lasers currently used for plasma X-ray sources can be conveniently and efficiently replaced by high average power and repetition rate laser radiation, as a way to increase the brightness of the generated X-rays.

Jerk-level synchronous repetitive motion scheme with gradient-type and zeroing-type dynamics algorithms applied to dual-arm redundant robot system control

NASA Astrophysics Data System (ADS)

Chen, Dechao; Zhang, Yunong

2017-10-01

Dual-arm redundant robot systems are usually required to handle primary tasks, repetitively and synchronously in practical applications. In this paper, a jerk-level synchronous repetitive motion scheme is proposed to remedy the joint-angle drift phenomenon and achieve the synchronous control of a dual-arm redundant robot system. The proposed scheme is novelly resolved at jerk level, which makes the joint variables, i.e. joint angles, joint velocities and joint accelerations, smooth and bounded. In addition, two types of dynamics algorithms, i.e. gradient-type (G-type) and zeroing-type (Z-type) dynamics algorithms, for the design of repetitive motion variable vectors, are presented in detail with the corresponding circuit schematics. Subsequently, the proposed scheme is reformulated as two dynamical quadratic programs (DQPs) and further integrated into a unified DQP (UDQP) for the synchronous control of a dual-arm robot system. The optimal solution of the UDQP is found by the piecewise-linear projection equation neural network. Moreover, simulations and comparisons based on a six-degrees-of-freedom planar dual-arm redundant robot system substantiate the operation effectiveness and tracking accuracy of the robot system with the proposed scheme for repetitive motion and synchronous control.

Repetition Suppression in the Left Inferior Frontal Gyrus Predicts Tone Learning Performance.

PubMed

Asaridou, Salomi S; Takashima, Atsuko; Dediu, Dan; Hagoort, Peter; McQueen, James M

2016-06-01

Do individuals differ in how efficiently they process non-native sounds? To what extent do these differences relate to individual variability in sound-learning aptitude? We addressed these questions by assessing the sound-learning abilities of Dutch native speakers as they were trained on non-native tone contrasts. We used fMRI repetition suppression to the non-native tones to measure participants' neuronal processing efficiency before and after training. Although all participants improved in tone identification with training, there was large individual variability in learning performance. A repetition suppression effect to tone was found in the bilateral inferior frontal gyri (IFGs) before training. No whole-brain effect was found after training; a region-of-interest analysis, however, showed that, after training, repetition suppression to tone in the left IFG correlated positively with learning. That is, individuals who were better in learning the non-native tones showed larger repetition suppression in this area. Crucially, this was true even before training. These findings add to existing evidence that the left IFG plays an important role in sound learning and indicate that individual differences in learning aptitude stem from differences in the neuronal efficiency with which non-native sounds are processed. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Compact 1.5-GHz intra-burst repetition rate Yb-doped all-PM-fiber laser system for ablation-cooled material removal

NASA Astrophysics Data System (ADS)

Akcaalan, Onder; Kalaycioglu, Hamit; Ilday, F. Omer

Although fs fiber laser systems are powerful technologies for material and tissue processing, limited ablation rates and high energy are drawbacks. Recently, we identified a new regime of laser-material interaction, ablation-cooled laser material removal, where the repetition rate has to be high enough so that the targeted spot size cannot cool down substantially by heat conduction which scales down ablation threshold by several orders of magnitude and reduces thermal effects to the bulk of the target. This opens the door to simplified laser systems for processing. In order to exploit this regime in tissue processing, a compact all-PM-fiber laser amplifier system with an intra-burst repetition rate of 1.5 GHz is developed on a 40 x 65 cm platform. The system is able to produce bursts ranging from 20-ns to 65-ns duration with 20 uJ to 80 uJ total energy, respectively, and pulses with up to 2 uJ individual energy and burst repetition rate ranging from 25 kHz to 200 kHz. The seed signal is generated by a home-built all-normal dispersion oscillator with 385 MHz repetition rate and converted to approximately 1.5 GHz by a multiplier. Amplified pulses are compressed to approximately 250-fs, the shortest pulse width for burst-mode fiber laser systems known to date.

Effect of Bench Press Load Knowledge on Repetitions, Rating of Perceived Exertion, and Attentional Focus.

PubMed

Beaudoin, Christina M; Cox, Zachary; Dundore, Tyler; Thomas, Tayler; Kim, Johnathon; Pillivant, Daniel

2018-02-01

Beaudoin, CM, Cox, Z, Dundore, T, Thomas, T, Kim, J, and Pillivant, D. Effect of bench press load knowledge on repetitions, rating of perceived exertion, and attentional focus. J Strength Cond Res 32(2): 514-519, 2018-Few studies have examined the role of the teleoanticipation during resistance training. The purpose of this study was to examine the effect of bench press (BP) load knowledge on repetitions completed, ratings of perceived exertion (RPEs), and attentional focus (% associative). Thirty-six recreationally active resistance-trained men (n = 25) and women (n = 11) participated in this study (age = 20.97 ± 1.87 years; ht = 174.12 ± 9.41 cm; and mass = 80.14 ± 14.03 kg). All subjects completed 3 testing sessions: (a) 1 repetition maximum (1RM) BP determination; (b) submaximal BP repetitions to fatigue known load (KL); and (c) submaximal BP repetitions to fatigue unknown load (UL). Known load and UL sessions were randomized and counterbalanced and both completed at 70% 1RM. An estimated weight ratio was computed using the subject's estimate of the UL weight relative to the KL weight. An independent samples t-test revealed no significant testing order difference for the estimated weight ratio. Two-way repeated-measures analysis of variances revealed no significant differences in the number of repetitions (p = 0.63), RPE (p = 0.18), or attentional focus (% associative) (p = 0.93) between the KL and UL conditions. Pearson correlations found a moderate positive association between KL repetitions completed and % associative focus when the UL was completed before the KL. Load knowledge did not influence the number of repetitions, RPE, or attentional focus while completing the BP. Further research examining the use of pacing strategies, RPE, and attentional focus during KL and UL conditions are warranted.

A Retrieved Context Account of Spacing and Repetition Effects in Free Recall

ERIC Educational Resources Information Center

Siegel, Lynn L.; Kahana, Michael J.

2014-01-01

Repeating an item in a list benefits recall performance, and this benefit increases when the repetitions are spaced apart (Madigan, 1969; Melton, 1970). Retrieved context theory incorporates 2 mechanisms that account for these effects: contextual variability and study-phase retrieval. Specifically, if an item presented at position "i" is…

Attentional Modulation of Masked Repetition and Categorical Priming in Young and Older Adults

ERIC Educational Resources Information Center

Fabre, Ludovic; Lemaire, Patrick; Grainger, Jonathan

2007-01-01

Three experiments examined the effects of temporal attention and aging on masked repetition and categorical priming for numbers and words. Participants' temporal attention was manipulated by varying the stimulus onset asynchrony (i.e., constant or variable SOA). In Experiment 1, participants performed a parity judgment task and a lexical decision…

High stimulus variability in nonnative speech learning supports formation of abstract categories: evidence from Japanese geminates.

PubMed

Sadakata, Makiko; McQueen, James M

2013-08-01

This study reports effects of a high-variability training procedure on nonnative learning of a Japanese geminate-singleton fricative contrast. Thirty native speakers of Dutch took part in a 5-day training procedure in which they identified geminate and singleton variants of the Japanese fricative /s/. Participants were trained with either many repetitions of a limited set of words recorded by a single speaker (low-variability training) or with fewer repetitions of a more variable set of words recorded by multiple speakers (high-variability training). Both types of training enhanced identification of speech but not of nonspeech materials, indicating that learning was domain specific. High-variability training led to superior performance in identification but not in discrimination tests, and supported better generalization of learning as shown by transfer from the trained fricatives to the identification of untrained stops and affricates. Variability thus helps nonnative listeners to form abstract categories rather than to enhance early acoustic analysis.

Trainer variability during step training after spinal cord injury: Implications for robotic gait-training device design.

PubMed

Galvez, Jose A; Budovitch, Amy; Harkema, Susan J; Reinkensmeyer, David J

2011-01-01

Robotic devices are being developed to automate repetitive aspects of walking retraining after neurological injuries, in part because they might improve the consistency and quality of training. However, it is unclear how inconsistent manual training actually is or whether stepping quality depends strongly on the trainers' manual skill. The objective of this study was to quantify trainer variability of manual skill during step training using body-weight support on a treadmill and assess factors of trainer skill. We attached a sensorized orthosis to one leg of each patient with spinal cord injury and measured the shank kinematics and forces exerted by different trainers during six training sessions. An expert trainer rated the trainers' skill level based on videotape recordings. Between-trainer force variability was substantial, about two times greater than within-trainer variability. Trainer skill rating correlated strongly with two gait features: better knee extension during stance and fewer episodes of toe dragging. Better knee extension correlated directly with larger knee horizontal assistance force, but better toe clearance did not correlate with larger ankle push-up force; rather, it correlated with better knee and hip extension. These results are useful to inform robotic gait-training design.

Processing new and repeated names: Effects of coreference on repetition priming with speech and fast RSVP

PubMed Central

Camblin, C. Christine; Ledoux, Kerry; Boudewyn, Megan; Gordon, Peter C.; Swaab, Tamara Y.

2006-01-01

Previous research has shown that the process of establishing coreference with a repeated name can affect basic repetition priming. Specifically, repetition priming on some measures can be eliminated for repeated names that corefer with an entity that is prominent in the discourse model. However, the exact nature and timing of this modulating effect of discourse are not yet understood. Here, we present two ERP studies that further probe the nature of repeated name coreference by using naturally produced connected speech and fast-rate RSVP methods of presentation. With speech we found that repetition priming was eliminated for repeated names that coreferred with a prominent antecedent. In contrast, with fast-rate RSVP, we found a main effect of repetition that did not interact with sentence context. This indicates that the creation of a discourse model during comprehension can affect repetition priming, but the nature of this effect may depend on input speed. PMID:16904078

Left hemisphere specialization for the control of voluntary movement rate.

PubMed

Agnew, John A; Zeffiro, Thomas A; Eden, Guinevere F

2004-05-01

Although persuasive behavioral evidence demonstrates the superior dexterity of the right hand in most people under a variety of conditions, little is known about the neural mechanisms responsible for this phenomenon. As this lateralized superiority is most evident during the performance of repetitive, speeded movement, we used parametric rate variations to compare visually paced movement of the right and left hands. Twelve strongly right-handed subjects participated in a functional magnetic resonance imaging (fMRI) experiment involving variable rate thumb movements. For movements of the right hand, contralateral rate-related activity changes were identified in the precentral gyrus, thalamus, and posterior putamen. For left-hand movements, activity was seen only in the contralateral precentral gyrus, consistent with the existence of a rate-sensitive motor control subsystem involving the left, but not the right, medial premotor corticostriatal loop in right-handed individuals. We hypothesize that the right hemisphere system is less skilled at controlling variable-rate movements and becomes maximally engaged at a lower movement rate without further modulation. These findings demonstrate that right- and left-hand movements engage different neural systems to control movement, even during a relatively simple thumb flexion task. Specialization of the left hemisphere corticostriatal system for dexterity is reflected in asymmetric mechanisms for movement rate control.

Ultrahigh-Repetition Pulse Train with Absolute-Phase Control Produced by AN Adiabatic Raman Process

NASA Astrophysics Data System (ADS)

Katsuragawa, M.; Suzuki, T.; Shiraga, K.; Arakawa, M.; Onose, T.; Yokoyama, K.; Hong, F. L.; Misawa, K.

2010-02-01

We describe the generation of an ultrahigh-repetition-rate train of ultrashort pulses on the basis of an adiabatic Raman process. We also describe recent progress in studies toward the ultimate regime: realization of an ultrahigh-repetition-rate train of monocycle pulses with control of the absolute phase. We comment on the milestones expected in the near future in terms of the study of such novel light sources and the new field of optical science stimulated by their development.

Study of a plate-electrode XeCl laser with a pulse repetition rate up to 5 kHz

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

Voevodin, Denis D; Vysotskii, Andrei V; Lazhintsev, Boris V

2012-11-30

The results of the study of a repetitively pulsed XeCl laser with a high rate of pulse repetition and the electrode assembly based on a multi-section discharge gap with inductance-capacitance stabilisation of the discharge are presented. The multi-section discharge gap is formed by 25 pairs of anode - cathode plates. The discharge formed in the interelectrode gap had the dimensions 250 Multiplication-Sign 12 Multiplication-Sign 2 mm. The studies were performed using the HCl - Xe - Ne laser mixture at the total pressure up to 3.5 atm. The limit value of the radiation pulse repetition rate was equal to 5more » kHz. The meansquare deviation of the pulse energy increased from 0.8 % to 1.6 % in the range of repetition rates from 1 to 4.5 kHz and did not exceed 2.4 % at the frequency 5 kHz. The maximal energy of the laser pulse and the efficiency coefficient were equal to 7.9 mJ and 1.6 %, respectively. The maximal power of laser radiation (31 W) was obtained at the repetition rate 5 kHz. A new technique of measuring the gas flow velocity in the interelectrode gap is proposed. The velocity of gas circulation at the maximal pressure of the mixture did not exceed 18 m s{sup -1}. Optical inhomogeneities were observed, caused by a high concentration of electrons in the discharge plasma, by the acoustic wave, arising in the discharge gap, and by the heating of the gas in the discharge. (lasers)« less

Repeating with the right hemisphere: reduced interactions between phonological and lexical-semantic systems in crossed aphasia?

PubMed Central

De-Torres, Irene; Dávila, Guadalupe; Berthier, Marcelo L.; Walsh, Seán Froudist; Moreno-Torres, Ignacio; Ruiz-Cruces, Rafael

2013-01-01

Knowledge on the patterns of repetition amongst individuals who develop language deficits in association with right hemisphere lesions (crossed aphasia) is very limited. Available data indicate that repetition in some crossed aphasics experiencing phonological processing deficits is not heavily influenced by lexical-semantic variables (lexicality, imageability, and frequency) as is regularly reported in phonologically-impaired cases with left hemisphere damage. Moreover, in view of the fact that crossed aphasia is rare, information on the role of right cortical areas and white matter tracts underpinning language repetition deficits is scarce. In this study, repetition performance was assessed in two patients with crossed conduction aphasia and striatal/capsular vascular lesions encompassing the right arcuate fasciculus (AF) and inferior frontal-occipital fasciculus (IFOF), the temporal stem and the white matter underneath the supramarginal gyrus. Both patients showed lexicality effects repeating better words than non-words, but manipulation of other lexical-semantic variables exerted less influence on repetition performance. Imageability and frequency effects, production of meaning-based paraphrases during sentence repetition, or better performance on repeating novel sentences than overlearned clichés were hardly ever observed in these two patients. In one patient, diffusion tensor imaging disclosed damage to the right long direct segment of the AF and IFOF with relative sparing of the anterior indirect and posterior segments of the AF, together with fully developed left perisylvian white matter pathways. These findings suggest that striatal/capsular lesions extending into the right AF and IFOF in some individuals with right hemisphere language dominance are associated with atypical repetition patterns which might reflect reduced interactions between phonological and lexical-semantic processes. PMID:24151460

300-MHz-repetition-rate, all-fiber, femtosecond laser mode-locked by planar lightwave circuit-based saturable absorber.

PubMed

Kim, Chur; Kim, Dohyun; Cheong, YeonJoon; Kwon, Dohyeon; Choi, Sun Young; Jeong, Hwanseong; Cha, Sang Jun; Lee, Jeong-Woo; Yeom, Dong-Il; Rotermund, Fabian; Kim, Jungwon

2015-10-05

We show the implementation of fiber-pigtailed, evanescent-field-interacting, single-walled carbon nanotube (CNT)-based saturable absorbers (SAs) using standard planar lightwave circuit (PLC) fabrication processes. The implemented PLC-CNT-SA device is employed to realize self-starting, high-repetition-rate, all-fiber ring oscillators at telecommunication wavelength. We demonstrate all-fiber Er ring lasers operating at 303-MHz (soliton regime) and 274-MHz (stretched-pulse regime) repetition-rates. The 303-MHz (274-MHz) laser centered at 1555 nm (1550 nm) provides 7.5 nm (19 nm) spectral bandwidth. After extra-cavity amplilfication, the amplified pulse train of the 303-MHz (274-MHz) laser delivers 209 fs (178 fs) pulses. To our knowledge, this corresponds to the highest repetition-rates achieved for femtosecond lasers employing evanescent-field-interacting SAs. The demonstrated SA fabrication method, which is based on well-established PLC processes, also shows a potential way for mass-producible and lower-cost waveguide-type SA devices suitable for all-fiber and waveguide lasers.

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

PubMed Central

Green, B.; Kovalev, S.; Asgekar, V.; Geloni, G.; Lehnert, U.; Golz, T.; Kuntzsch, M.; Bauer, C.; Hauser, J.; Voigtlaender, J.; Wustmann, B.; Koesterke, I.; Schwarz, M.; Freitag, M.; Arnold, A.; Teichert, J.; Justus, M.; Seidel, W.; Ilgner, C.; Awari, N.; Nicoletti, D.; Kaiser, S.; Laplace, Y.; Rajasekaran, S.; Zhang, L.; Winnerl, S.; Schneider, H.; Schay, G.; Lorincz, I.; Rauscher, A. A.; Radu, I.; Mährlein, S.; Kim, T. H.; Lee, J. S.; Kampfrath, T.; Wall, S.; Heberle, J.; Malnasi-Csizmadia, A.; Steiger, A.; Müller, A. S.; Helm, M.; Schramm, U.; Cowan, T.; Michel, P.; Cavalleri, A.; Fisher, A. S.; Stojanovic, N.; Gensch, M.

2016-01-01

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields and the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. We benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution. PMID:26924651

Optimization and phase matching of fiber-laser-driven high-order harmonic generation at high repetition rate.

PubMed

Cabasse, Amélie; Machinet, Guillaume; Dubrouil, Antoine; Cormier, Eric; Constant, Eric

2012-11-15

High-repetition-rate sources are very attractive for high-order harmonic generation (HHG). However, due to their pulse characteristics (low energy, long duration), those systems require a tight focusing geometry to achieve the necessary intensity to generate harmonics. In this Letter, we investigate theoretically and experimentally the optimization of HHG in this geometry, to maximize the extreme UV (XUV) photon flux and improve the conversion efficiency. We analyze the influence of atomic gas media (Ar, Kr, or Xe), gas pressure, and interaction geometries (a gas jet and a finite and a semi-infinite gas cell). Numerical simulations allow us to define optimal conditions for HHG in this tight focusing regime and to observe the signature of on-axis phase matching. These conditions are implemented experimentally using a high-repetition-rate Yb-doped fiber laser system. We achieve optimization of emission with a recorded XUV photon flux of 4.5×10(12) photons/s generated in Xe at 100 kHz repetition rate.

Offset frequency dynamics and phase noise properties of a self-referenced 10 GHz Ti:sapphire frequency comb.

PubMed

Heinecke, Dirk C; Bartels, Albrecht; Diddams, Scott A

2011-09-12

This paper shows the experimental details of the stabilization scheme that allows full control of the repetition rate and the carrier-envelope offset frequency of a 10 GHz frequency comb based on a femtosecond Ti:sapphire laser. Octave-spanning spectra are produced in nonlinear microstructured optical fiber, in spite of the reduced peak power associated with the 10 GHz repetition rate. Improved stability of the broadened spectrum is obtained by temperature-stabilization of the nonlinear optical fiber. The carrier-envelope offset frequency and the repetition rate are simultaneously frequency stabilized, and their short- and long-term stabilities are characterized. We also measure the transfer of amplitude noise of the pump source to phase noise on the offset frequency and verify an increased sensitivity of the offset frequency to pump power modulation compared to systems with lower repetition rate. Finally, we discuss merits of this 10 GHz system for the generation of low-phase-noise microwaves from the photodetected pulse train.

High-Field High-Repetition-Rate Sources for the Coherent THz Control of Matter

DOE PAGES

Green, B.; Kovalev, S.; Asgekar, V.; ...

2016-02-29

Ultrashort flashes of THz light with low photon energies of a few meV, but strong electric or magnetic field transients have recently been employed to prepare various fascinating nonequilibrium states in matter. Here we present a new class of sources based on superradiant enhancement of radiation from relativistic electron bunches in a compact electron accelerator that we believe will revolutionize experiments in this field. Our prototype source generates high-field THz pulses at unprecedented quasi-continuous-wave repetition rates up to the MHz regime. We demonstrate parameters that exceed state-of-the-art laser-based sources by more than 2 orders of magnitude. The peak fields andmore » the repetition rates are highly scalable and once fully operational this type of sources will routinely provide 1 MV/cm electric fields and 0.3 T magnetic fields at repetition rates of few 100 kHz. In conclusion, we benchmark the unique properties by performing a resonant coherent THz control experiment with few 10 fs resolution.« less

Ultrafast, high repetition rate, ultraviolet, fiber-laser-based source: application towards Yb⁺ fast quantum-logic.

PubMed

Hussain, Mahmood Irtiza; Petrasiunas, Matthew Joseph; Bentley, Christopher D B; Taylor, Richard L; Carvalho, André R R; Hope, Joseph J; Streed, Erik W; Lobino, Mirko; Kielpinski, David

2016-07-25

Trapped ions are one of the most promising approaches for the realization of a universal quantum computer. Faster quantum logic gates could dramatically improve the performance of trapped-ion quantum computers, and require the development of suitable high repetition rate pulsed lasers. Here we report on a robust frequency upconverted fiber laser based source, able to deliver 2.5 ps ultraviolet (UV) pulses at a stabilized repetition rate of 300.00000 MHz with an average power of 190 mW. The laser wavelength is resonant with the strong transition in Ytterbium (Yb⁺) at 369.53 nm and its repetition rate can be scaled up using high harmonic mode locking. We show that our source can produce arbitrary pulse patterns using a programmable pulse pattern generator and fast modulating components. Finally, simulations demonstrate that our laser is capable of performing resonant, temperature-insensitive, two-qubit quantum logic gates on trapped Yb⁺ ions faster than the trap period and with fidelity above 99%.

Thermal limits on MV x-ray production by bremsstrahlung targets in the context of novel linear accelerators.

PubMed

Wang, Jinghui; Trovati, Stefania; Borchard, Philipp M; Loo, Billy W; Maxim, Peter G; Fahrig, Rebecca

2017-12-01

To study the impact of target geometrical and linac operational parameters, such as target material and thickness, electron beam size, repetition rate, and mean current on the ability of the radiotherapy treatment head to deliver high-dose-rate x-ray irradiation in the context of novel linear accelerators capable of higher repetition rates/duty cycle than conventional clinical linacs. The depth dose in a water phantom without a flattening filter and heat deposition in an x-ray target by 10 MeV pulsed electron beams were calculated using the Monte-Carlo code MCNPX, and the transient temperature behavior of the target was simulated by ANSYS. Several parameters that affect both the dose distribution and temperature behavior were investigated. The target was tungsten with a thickness ranging from 0 to 3 mm and a copper heat remover layer. An electron beam with full width at half maximum (FWHM) between 0 and3 mm and mean current of 0.05-2 mA was used as the primary beam at repetition rates of 100, 200, 400, and 800 Hz. For a 10 MeV electron beam with FWHM of 1 mm, pulse length of 5 μs, by using a thin tungsten target with thickness of 0.2 mm instead of 1 mm, and by employing a high repetition rate of 800 Hz instead of 100 Hz, the maximum dose rate delivered can increase two times from 0.57 to 1.16 Gy/s. In this simple model, the limiting factor on dose rate is the copper heat remover's softening temperature, which was considered to be 500°C in our study. A high dose rate can be obtained by employing thin targets together with high repetition rate electron beams enabled by novel linac designs, whereas the benefit of thin targets is marginal at conventional repetition rates. Next generation linacs used to increase dose rate need different target designs compared to conventional linacs. © 2017 American Association of Physicists in Medicine.

Rest Interval Required for Power Training With Power Load in the Bench Press Throw Exercise.

PubMed

Hernández Davó, Jose L; Solana, Rafael Sabido; Sarabia Marín, Jose M; Fernández Fernández, Jaime; Moya Ramón, Manuel

2016-05-01

This study aimed to test the influence of various rest interval (RI) durations used between sets on power output performance and physiological and perceptual variables during a strength training session using 40% of the 1 repetition maximum (1RM) in the bench press throw exercise. Thirty-one college students (18 males and 13 females) took part in the study. The experimental protocol consists of 5 sets of 8 repetitions of the bench press throw exercise with a load representing 40% of 1RM. Subjects performed the experimental protocol on 3 different occasions, differing by the RI between sets (1, 2, or 3 minutes). During the sessions, power data (mean power and peak power), physiological (lactate concentration [La]) and perceptual (rating of perceived exertion) variables were measured. In addition, delayed onset muscular soreness was reported 24 and 48 hours after the training session. One-way repeated-measures analysis of variance showed that 1-minute RI entailed higher power decreases and greater increases in values of physiological and perceptual variables compared with both 2- and 3-minute RIs. Nevertheless, no differences were found between 2- and 3-minute RIs. Therefore, this study showed that, when training with 40% of 1RM in the bench press throw exercise, a 2-minute RI between sets can be enough to avoid significant decreases in power output. Consequently, training sessions' duration could be reduced without causing excessive fatigue, allowing additional time to focus on other conditioning priorities.

Investigation of a reacting jet injected into vitiated crossflow using CARS, high repetition rate OH-PLIF, and high repetition rate PIV

NASA Astrophysics Data System (ADS)

Roa, Mario

The proposed PhD thesis research program will be carried out in a staged combustion test rig developed with funding from Siemens Power Generation Inc. and the United States Department of Energy. This research program will study the reacting flow field created by an injector that is axially distributed along the combustor with use the laser diagnostics methods: Coherent Anti-Stokes Raman Spectroscopy (CARS), high repetition rate OH Planar Laser Induced Florescence (OHPLIF), and high repetition rate Particle Image Velocimetry (PIV), to determine why certain conditions result in low NOx emissions. This data will be used to validated the development of more precise computer models. These laser diagnostic techniques will be applied to the reacting jet produced using an extended, premixed 10 mm injector using both natural gas (NG) and hydrogen (H2) as fuels. The objective of this thesis research is to use advance laser diagnostics to gain insight into the reacting flow field resulting form transverse injection into a vitiated cross flow. The advance laser diagnostics will also provide insight into pollution formation mechanisms and will be used for validating CFD models of the transverse jet injection. The following measurements will be performed: (1) dual pump nitrogen/hydrogen (H2/ N2) CARS at the midplane of the extended 10 mm nozzle, (2) high repetition rate OH-PLIF and emission sampling for the same extended nozzle using NG and H2 as secondary fuel, (3) and combing both high repetition OH-PLIF and high repetition rate PIV for extended 10 mm nozzle for both NG and H2 secondary fuel. The PIV measurements will be combined with OH-PLIF in a simultaneous manner, with the OH fluorescence centered between the two PIV laser pulses. The dual pump H2/N2 CARS system will be used to measure both temperature of the reacting jet and the species concentration ratio of H2/ N2. The high repetition rate OH-PLIF, conducted with a 5 kHz, dual cavity Nd:YAG laser that optically pumps a dye laser tuned to the Q1(7) OH florescence transition. It will be used to visualize the flame front of the reacting jet. The high repetition rate PIV will be performed with a dual cavity laser at 10 kHz. High repetition rate PIV will be used to characterize the velocity and vortical structures produced in the reacting flow field. This research project will aid in the understanding of NOx creation in an staged gas turbine combustor and provide crucial data that will be used to develop precise computer models that will be used in designing the next power generation gas turbines. As power generation turbines increase in usage in future due to the abundance of NG as a fuel source or H 2 gas produced via green energy policies, it will be vital to make these new generation turbines more efficient and further reduce pollutant emission levels.

Contribution of fronto-striatal regions to emotional valence and repetition under cognitive conflict.

PubMed

Chun, Ji-Won; Park, Hae-Jeong; Kim, Dai Jin; Kim, Eosu; Kim, Jae-Jin

2017-07-01

Conflict processing mediated by fronto-striatal regions may be influenced by emotional properties of stimuli. This study aimed to examine the effects of emotion repetition on cognitive control in a conflict-provoking situation. Twenty-one healthy subjects were scanned using functional magnetic resonance imaging while performing a sequential cognitive conflict task composed of emotional stimuli. The regional effects were analyzed according to the repetition or non-repetition of cognitive congruency and emotional valence between the preceding and current trials. Post-incongruence interference in error rate and reaction time was significantly smaller than post-congruence interference, particularly under repeated positive and non-repeated positive, respectively, and post-incongruence interference, compared to post-congruence interference, increased activity in the ACC, DLPFC, and striatum. ACC and DLPFC activities were significantly correlated with error rate or reaction time in some conditions, and fronto-striatal connections were related to the conflict processing heightened by negative emotion. These findings suggest that the repetition of emotional stimuli adaptively regulates cognitive control and the fronto-striatal circuit may engage in the conflict adaptation process induced by emotion repetition. Both repetition enhancement and repetition suppression of prefrontal activity may underlie the relationship between emotion and conflict adaptation. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Harmonic mode-locking using the double interval technique in quantum dot lasers.

PubMed

Li, Yan; Chiragh, Furqan L; Xin, Yong-Chun; Lin, Chang-Yi; Kim, Junghoon; Christodoulou, Christos G; Lester, Luke F

2010-07-05

Passive harmonic mode-locking in a quantum dot laser is realized using the double interval technique, which uses two separate absorbers to stimulate a specific higher-order repetition rate compared to the fundamental. Operating alone these absorbers would otherwise reinforce lower harmonic frequencies, but by operating together they produce the harmonic corresponding to their least common multiple. Mode-locking at a nominal 60 GHz repetition rate, which is the 10(th) harmonic of the fundamental frequency of the device, is achieved unambiguously despite the constraint of a uniformly-segmented, multi-section device layout. The diversity of repetition rates available with this method is also discussed.

280  GHz dark soliton fiber laser.

PubMed

Song, Y F; Guo, J; Zhao, L M; Shen, D Y; Tang, D Y

2014-06-15

We report on an ultrahigh repetition rate dark soliton fiber laser. We show both numerically and experimentally that by taking advantage of the cavity self-induced modulation instability and the dark soliton formation in a net normal dispersion cavity fiber laser, stable ultrahigh repetition rate dark soliton trains can be formed in a dispersion-managed cavity fiber laser. Stable dark soliton trains with a repetition rate as high as ∼280  GHz have been generated in our experiment. Numerical simulations have shown that the effective gain bandwidth limitation plays an important role on the stabilization of the formed dark solitons in the laser.

A Real-Time Terahertz Time-Domain Polarization Analyzer with 80-MHz Repetition-Rate Femtosecond Laser Pulses

PubMed Central

Watanabe, Shinichi; Yasumatsu, Naoya; Oguchi, Kenichi; Takeda, Masatoshi; Suzuki, Takeshi; Tachizaki, Takehiro

2013-01-01

We have developed a real-time terahertz time-domain polarization analyzer by using 80-MHz repetition-rate femtosecond laser pulses. Our technique is based on the spinning electro-optic sensor method, which we recently proposed and demonstrated by using a regenerative amplifier laser system; here we improve the detection scheme in order to be able to use it with a femtosecond laser oscillator with laser pulses of a much higher repetition rate. This improvement brings great advantages for realizing broadband, compact and stable real-time terahertz time-domain polarization measurement systems for scientific and industrial applications. PMID:23478599

Frequency and predictors of courses repetition, probation, and delayed graduation in kashan faculty of nursing and midwifery.

PubMed

Tagharrobi, Zahra; Masoudi Alavi, Negin; Fakharian, Esmail; Mirhoseini, Fakhrossadat; Rasoulinejad, Sayyed Asghar; Akbari, Hossein; Ameli, Hossein

2013-12-01

Course failing and delayed graduation are important concerns in educational systems. The reasons of these educational failures need to be clarified. This study was designed to determine the academic failure rate and its predictors in Nursing and Midwifery Students in Kashan University of Medical Sciences. In this cross-sectional study, the records of all the students graduated in Nursing and Midwifery faculty during 18 years (1986 - 2003) were evaluated (1174 graduates). The demographic variables and the educational situation were recorded. The frequency of course repetition, probation, and delayed graduation were determined and the data were analyzed using the chi-square and logistic regression tests. The frequency of course repetition, probation, and delayed graduation was reported to be 19.25%, 3.9% and 19.85%, respectively. Gaining Low grade in high school, transferring from other universities, having special quota, and transferring temporarily to other universities were mentioned as the risk factors of academic failure. The major had a significant relationship with academic failure. Day time students had more course failure and night time students stayed longer in the university. The individual characteristics, educational background and admission criteria had showed relation with academic failure. Vulnerable students should be identified and educational supports should be provided for these students.

Chronic Effects of Different Rest Intervals Between Sets on Dynamic and Isometric Muscle Strength and Muscle Activity in Trained Older Women.

PubMed

Jambassi Filho, José Claudio; Gurjão, André Luiz Demantova; Ceccato, Marilia; Prado, Alexandre Konig Garcia; Gallo, Luiza Herminia; Gobbi, Sebastião

2017-09-01

This study investigated the chronic effects of different rest intervals (RIs) between sets on dynamic and isometric muscle strength and muscle activity. We used a repeated-measures design (pretraining and posttraining) with independent groups (different RI). Twenty-one resistance-trained older women (66.4 ± 4.4 years) were randomly assigned to either a 1-minute RI group (G-1 min; n = 10) or 3-minute RI group (G-3 min; n = 11). Both groups completed 3 supervised sessions per week during 8 weeks. In each session, participants performed 3 sets of 15 repetitions of leg press exercise, with a load that elicited muscle failure in the third set. Fifteen maximum repetitions, maximal voluntary contraction, peak rate of force development, and integrated electromyography activity of the vastus lateralis and vastus medialis muscles were assessed pretraining and posttraining. There was a significant increase in load of 15 maximum repetitions posttraining for G-3 min only (3.6%; P < 0.05). However, posttraining results showed no significant differences between G-1 min and G-3 min groups for all dependent variables (P > 0.05). The findings suggest that different RIs between sets did not influence dynamic and isometric muscle strength and muscle activity in resistance-trained older women.

Theoretical repeatability assessment without repetitive measurements in gradient high-performance liquid chromatography.

PubMed

Kotani, Akira; Tsutsumi, Risa; Shoji, Asaki; Hayashi, Yuzuru; Kusu, Fumiyo; Yamamoto, Kazuhiro; Hakamata, Hideki

2016-07-08

This paper puts forward a time and material-saving method for evaluating the repeatability of area measurements in gradient HPLC with UV detection (HPLC-UV), based on the function of mutual information (FUMI) theory which can theoretically provide the measurement standard deviation (SD) and detection limits through the stochastic properties of baseline noise with no recourse to repetitive measurements of real samples. The chromatographic determination of terbinafine hydrochloride and enalapril maleate is taken as an example. The best choice of the number of noise data points, inevitable for the theoretical evaluation, is shown to be 512 data points (10.24s at 50 point/s sampling rate of an A/D converter). Coupled with the relative SD (RSD) of sample injection variability in the instrument used, the theoretical evaluation is proved to give identical values of area measurement RSDs to those estimated by the usual repetitive method (n=6) over a wide concentration range of the analytes within the 95% confidence intervals of the latter RSD. The FUMI theory is not a statistical one, but the "statistical" reliability of its SD estimates (n=1) is observed to be as high as that attained by thirty-one measurements of the same samples (n=31). Copyright © 2016 Elsevier B.V. All rights reserved.

Novel underwater soundscape: acoustic repertoire of plainfin midshipman fish.

PubMed

McIver, Eileen L; Marchaterre, Margaret A; Rice, Aaron N; Bass, Andrew H

2014-07-01

Toadfishes are among the best-known groups of sound-producing (vocal) fishes and include species commonly known as toadfish and midshipman. Although midshipman have been the subject of extensive investigation of the neural mechanisms of vocalization, this is the first comprehensive, quantitative analysis of the spectro-temporal characters of their acoustic signals and one of the few for fishes in general. Field recordings of territorial, nest-guarding male midshipman during the breeding season identified a diverse vocal repertoire composed of three basic sound types that varied widely in duration, harmonic structure and degree of amplitude modulation (AM): 'hum', 'grunt' and 'growl'. Hum duration varied nearly 1000-fold, lasting for minutes at a time, with stable harmonic stacks and little envelope modulation throughout the sound. By contrast, grunts were brief, ~30-140 ms, broadband signals produced both in isolation and repetitively as a train of up to 200 at intervals of ~0.5-1.0 s. Growls were also produced alone or repetitively, but at variable intervals of the order of seconds with durations between those of grunts and hums, ranging 60-fold from ~200 ms to 12 s. Growls exhibited prominent harmonics with sudden shifts in pulse repetition rate and highly variable AM patterns, unlike the nearly constant AM of grunt trains and flat envelope of hums. Behavioral and neurophysiological studies support the hypothesis that each sound type's unique acoustic signature contributes to signal recognition mechanisms. Nocturnal production of these sounds against a background chorus dominated constantly for hours by a single sound type, the multi-harmonic hum, reveals a novel underwater soundscape for fish. © 2014. Published by The Company of Biologists Ltd.

The Effect of Speech Repetition Rate on Neural Activation in Healthy Adults: Implications for Treatment of Aphasia and Other Fluency Disorders.

PubMed

Marchina, Sarah; Norton, Andrea; Kumar, Sandeep; Schlaug, Gottfried

2018-01-01

Functional imaging studies have provided insight into the effect of rate on production of syllables, pseudowords, and naturalistic speech, but the influence of rate on repetition of commonly-used words/phrases suitable for therapeutic use merits closer examination. Aim: To identify speech-motor regions responsive to rate and test the hypothesis that those regions would provide greater support as rates increase, we used an overt speech repetition task and functional magnetic resonance imaging (fMRI) to capture rate-modulated activation within speech-motor regions and determine whether modulations occur linearly and/or show hemispheric preference. Methods: Twelve healthy, right-handed adults participated in an fMRI task requiring overt repetition of commonly-used words/phrases at rates of 1, 2, and 3 syllables/second (syll./sec.). Results: Across all rates, bilateral activation was found both in ventral portions of primary sensorimotor cortex and middle and superior temporal regions. A repeated measures analysis of variance with pairwise comparisons revealed an overall difference between rates in temporal lobe regions of interest (ROIs) bilaterally ( p < 0.001); all six comparisons reached significance ( p < 0.05). Five of the six were highly significant ( p < 0.008), while the left-hemisphere 2- vs. 3-syll./sec. comparison, though still significant, was less robust ( p = 0.037). Temporal ROI mean beta-values increased linearly across the three rates bilaterally. Significant rate effects observed in the temporal lobes were slightly more pronounced in the right-hemisphere. No significant overall rate differences were seen in sensorimotor ROIs, nor was there a clear hemispheric effect. Conclusion: Linear effects in superior temporal ROIs suggest that sensory feedback corresponds directly to task demands. The lesser degree of significance in left-hemisphere activation at the faster, closer-to-normal rate may represent an increase in neural efficiency (and therefore, decreased demand) when the task so closely approximates a highly-practiced function. The presence of significant bilateral activation during overt repetition of words/phrases at all three rates suggests that repetition-based speech production may draw support from either or both hemispheres. This bihemispheric redundancy in regions associated with speech-motor control and their sensitivity to changes in rate may play an important role in interventions for nonfluent aphasia and other fluency disorders, particularly when right-hemisphere structures are the sole remaining pathway for production of meaningful speech.

Bilingual Children's Performance on Three Nonword Repetition Tasks: The Role of Language Experience and Ability

ERIC Educational Resources Information Center

Huls, Simone

2017-01-01

Nonword repetition (NWR) tasks represent one assessment tool for Specific Language Impairment (SLI). The use of such tasks has been established and verified for monolingual children. However, the diagnostic accuracy of NWR tasks for bilingual children has had variable results and must address several unique characteristics of this population. Gaps…

A long-pulse repetitive operation magnetically insulated transmission line oscillator.

PubMed

Fan, Yu-Wei; Zhong, Hui-Huang; Zhang, Jian-De; Shu, Ting; Liu, Jin Liang

2014-05-01

The improved magnetically insulated transmission line oscillator (MILO) is a gigawatt-class L-band high power microwave tube. It has allowed us to generate 3.1 GW pulse of 40 ns duration in the single-pulse operation and 500 MW pulse of 25 ns duration in the repetition rate operation. However, because of the severe impedance mismatch, the power conversion efficiency is only about 4% in the repetition rate operation. In order to eliminate the impedance mismatch and obtain repetitive long-pulse high-power microwave (HPM), a series of experiments are carried out and the recent progress is presented in this paper. In the single-pulse operation, when the diode voltage is 466 kV and current is 41.6 kA, the radiated microwave power is above 2.2 GW, the pulse duration is above 102 ns, the microwave frequency is about 1.74 GHz, and the power conversion efficiency is about 11.5%. In the repetition rate operation, under the condition of the diode voltage about 400 kV, beam current about 38 kA, the radiated microwave power is about 1.0 GW, the pulse duration is about 85 ns. Moreover, the radiated microwave power and the pulse duration decline little by little when the shot numbers increase gradually. The experimental results show that the impedance matching is a vital factor for HPM systems and one of the major technical challenges is to improve the cathode for the repetition rate operation MILO.

Switching between simple cognitive tasks: the interaction of top-down and bottom-up factors

NASA Technical Reports Server (NTRS)

Ruthruff, E.; Remington, R. W.; Johnston, J. C.

2001-01-01

How do top-down factors (e.g., task expectancy) and bottom-up factors (e.g., task recency) interact to produce an overall level of task readiness? This question was addressed by factorially manipulating task expectancy and task repetition in a task-switching paradigm. The effects of expectancy and repetition on response time tended to interact underadditively, but only because the traditional binary task-repetition variable lumps together all switch trials, ignoring variation in task lag. When the task-recency variable was scaled continuously, all 4 experiments instead showed additivity between expectancy and recency. The results indicated that expectancy and recency influence different stages of mental processing. One specific possibility (the configuration-execution model) is that task expectancy affects the time required to configure upcoming central operations, whereas task recency affects the time required to actually execute those central operations.

The Effect of Syllable Repetition Rate on Vocal Characteristics

ERIC Educational Resources Information Center

Topbas, Oya; Orlikoff, Robert F.; St. Louis, Kenneth O.

2012-01-01

This study examined whether mean vocal fundamental frequency ("F"[subscript 0]) or speech sound pressure level (SPL) varies with changes in syllable repetition rate. Twenty-four young adults (12 M and 12 F) repeated the syllables/p[inverted v]/,/p[inverted v]t[schwa]/, and/p[inverted v]t[schwa]k[schwa]/at a modeled "slow" rate of approximately one…

A gigawatt level repetitive rate adjustable magnetic pulse compressor.

PubMed

Li, Song; Gao, Jing-Ming; Yang, Han-Wu; Qian, Bao-Liang; Li, Ze-Xin

2015-08-01

In this paper, a gigawatt level repetitive rate adjustable magnetic pulse compressor is investigated both numerically and experimentally. The device has advantages of high power level, high repetitive rate achievability, and long lifetime reliability. Importantly, dominate parameters including the saturation time, the peak voltage, and even the compression ratio can be potentially adjusted continuously and reliably, which significantly expands the applicable area of the device and generators based on it. Specifically, a two-stage adjustable magnetic pulse compressor, utilized for charging the pulse forming network of a high power pulse generator, is designed with different compression ratios of 25 and 18 through an optimized design process. Equivalent circuit analysis shows that the modification of compression ratio can be achieved by just changing the turn number of the winding. At the same time, increasing inductance of the grounded inductor will decrease the peak voltage and delay the charging process. Based on these analyses, an adjustable compressor was built and studied experimentally in both the single shot mode and repetitive rate mode. Pulses with peak voltage of 60 kV and energy per pulse of 360 J were obtained in the experiment. The rise times of the pulses were compressed from 25 μs to 1 μs and from 18 μs to 1 μs, respectively, at repetitive rate of 20 Hz with good repeatability. Experimental results show reasonable agreement with analyses.

A novel trigger for pseudospark switch with high repetition rate, low jitter, and compact structure

NASA Astrophysics Data System (ADS)

Yan, Jiaqi; Shen, Saikang; Wang, Yanan; Zhang, Siyu; Cheng, Le; Ding, Weidong

2018-06-01

This paper presents the design and development of a trigger with a high repetition rate, low jitter, and compact structure for the pseudospark switch (PSS), which includes an improved Marx generator based on avalanche transistors and a corona-plasma trigger unit. The generator adopted a novel 3 × 12-stage Marx circuit based on avalanche transistors in which the failure rate of transistors in the first and second stages was significantly reduced by connecting the parallel capacitors compared to the previous similar generator. The reason for the improved performance was also discussed. The main parameters of output pulses were an amplitude of -7 kV, rise time of 6 ns, jitter of 0.2 ns, and repetition rate of 2 kHz. The corona-plasma trigger unit adopted BaTiO3 ceramics with high ɛr as the dielectric and was arranged in the hollow cathode of the PSS. The experiments of triggering a PSS prototype were conducted. The influence of anode voltage and pressure on the trigger delay and jitter was studied, and the minimum trigger jitter achieved <1 ns. This trigger worked for 107 shots at the repetition rate of 2 kHz continuously without obvious performance degradation and any failure of the generator. The main advantage of this trigger is the simultaneous combination of the high repetition rate, low jitter, long lifetime, and great simplicity in a compact structure.

Design and Development of High-Repetition-Rate Satellite Laser Ranging System

NASA Astrophysics Data System (ADS)

Choi, Eun-Jung; Bang, Seong-Cheol; Sung, Ki-Pyoung; Lim, Hyung-Chul; Jung, Chan-Gyu; Kim, In-Yeung; Choi, Jae-Seung

2015-09-01

The Accurate Ranging System for Geodetic Observation ? Mobile (ARGO-M) was successfully developed as the first Korean mobile Satellite Laser Ranging (SLR) system in 2012, and has joined in the International Laser Ranging Service (ILRS) tracking network, DAEdeoK (DAEK) station. The DAEK SLR station was approved as a validated station in April 2014, through the ILRS station ¡°data validation¡± process. The ARGO-M system is designed to enable 2 kHz laser ranging with millimeter-level precision for geodetic, remote sensing, navigation, and experimental satellites equipped with Laser Retroreflector Arrays (LRAs). In this paper, we present the design and development of a next generation high-repetition-rate SLR system for ARGO-M. The laser ranging rate up to 10 kHz is becoming an important issue in the SLR community to improve ranging precision. To implement high-repetition-rate SLR system, the High-repetition-rate SLR operation system (HSLR-10) was designed and developed using ARGO-M Range Gate Generator (A-RGG), so as to enable laser ranging from 50 Hz to 10 kHz. HSLR-10 includes both hardware controlling software and data post-processing software. This paper shows the design and development of key technologies of high-repetition-rate SLR system. The developed system was tested successfully at DAEK station and then moved to Sejong station, a new Korean SLR station, on July 1, 2015. HSLR-10 will begin normal operations at Sejong station in the near future.

Could autonomic system assessment be helpful in disorders of consciousness diagnosis? A neurophysiological study.

PubMed

Leo, Antonino; Naro, Antonino; Cannavò, Antonio; Pisani, Laura Rosa; Bruno, Rocco; Salviera, Carlo; Bramanti, Placido; Calabrò, Rocco Salvatore

2016-08-01

Although patients with chronic disorders of consciousness (DOC), including unresponsive wakefulness syndrome (UWS) and minimally conscious state (MCS), show a limited repertoire of awareness signs, owing to a large-scale cortico-thalamo-cortical functional disconnectivity, an activation of some cortical areas in response to relevant stimuli has been described by means of electrophysiological and functional neuroimaging approaches. In addition, cognitive processes associated with autonomic nervous system (ANS) responses elicited by nociceptive stimuli have been identified in some DOC patients. In an attempt to identify ANS functionality markers that could be useful in differentiating UWS and MCS individuals, we measured the amplitude, latency and γ-band power (γPOW) of ultra-late laser-evoked potentials (CLEPs) and skin reflex (SR), which both express some aspects of cognitive processes related to ANS functionality, besides other ANS parameters either during a 24(hh)-polygraphy or following a solid-state laser repetitive nociceptive stimulation. MCS showed physiological modification of vital signs (O2 saturation, hearth rate, hearth rate variability) throughout the night and a preservation of SR-γPOW, whereas UWS did not show significant variations. Following repetitive nociceptive stimulation, MCS patients had a significant increase in CLEP-γPOW, O2 saturation, hearth rate, and hearth rate variability, whereas UWS individuals did not show any significant change (but two patients, who reached high Coma Recovery Scale-Revised scores). Hence, our work suggests that a wide-spectrum electrophysiological evaluation of ANS functionality may support DOC differential diagnosis. Interestingly, the two above-mentioned UWS patients showed MCS-like vital sign modifications and electrophysiological pain responsiveness. It is therefore hypothesizable that our approach could be helpful in identifying residual aware autonomic system-related cognitive processes even in some UWS patients. Such issue draws the attention to either DOC clinical diagnosis or adequate pain treatment in DOC patients.

A feasible repetitive transcranial magnetic stimulation clinical protocol in migraine prevention.

PubMed

Zardouz, Shawn; Shi, Lei; Leung, Albert

2016-01-01

This case series was conducted to determine the clinical feasibility of a repetitive transcranial magnetic stimulation protocol for the prevention of migraine (with and without aura). Five patients with migraines underwent five repetitive transcranial magnetic stimulation sessions separated in 1- to 2-week intervals for a period of 2 months at a single tertiary medical center. Repetitive transcranial magnetic stimulation was applied to the left motor cortex with 2000 pulses (20 trains with 1s inter-train interval) delivered per session, at a frequency of 10 Hz and 80% resting motor threshold. Pre- and post-treatment numerical rating pain scales were collected, and percent reductions in intensity, frequency, and duration were generated. An average decrease in 37.8%, 32.1%, and 31.2% were noted in the intensity, frequency, and duration of migraines post-repetitive transcranial magnetic stimulation, respectively. A mean decrease in 1.9±1.0 (numerical rating pain scale ± standard deviation; range: 0.4-2.8) in headache intensity scores was noted after the repetitive transcranial magnetic stimulation sessions. The tested repetitive transcranial magnetic stimulation protocol is a well-tolerated, safe, and effective method for migraine prevention.

Evaluating the utility of two gestural discomfort evaluation methods

PubMed Central

Son, Minseok; Jung, Jaemoon; Park, Woojin

2017-01-01

Evaluating physical discomfort of designed gestures is important for creating safe and usable gesture-based interaction systems; yet, gestural discomfort evaluation has not been extensively studied in HCI, and few evaluation methods seem currently available whose utility has been experimentally confirmed. To address this, this study empirically demonstrated the utility of the subjective rating method after a small number of gesture repetitions (a maximum of four repetitions) in evaluating designed gestures in terms of physical discomfort resulting from prolonged, repetitive gesture use. The subjective rating method has been widely used in previous gesture studies but without empirical evidence on its utility. This study also proposed a gesture discomfort evaluation method based on an existing ergonomics posture evaluation tool (Rapid Upper Limb Assessment) and demonstrated its utility in evaluating designed gestures in terms of physical discomfort resulting from prolonged, repetitive gesture use. Rapid Upper Limb Assessment is an ergonomics postural analysis tool that quantifies the work-related musculoskeletal disorders risks for manual tasks, and has been hypothesized to be capable of correctly determining discomfort resulting from prolonged, repetitive gesture use. The two methods were evaluated through comparisons against a baseline method involving discomfort rating after actual prolonged, repetitive gesture use. Correlation analyses indicated that both methods were in good agreement with the baseline. The methods proposed in this study seem useful for predicting discomfort resulting from prolonged, repetitive gesture use, and are expected to help interaction designers create safe and usable gesture-based interaction systems. PMID:28423016

A compact, rugged, high repetition rate CO2 laser incorporating catalyst

NASA Technical Reports Server (NTRS)

Schwarzenberger, P. M.; Matzangou, X.

1990-01-01

The principal design features and operating characteristics of a high repetition rate CO2 laser are outlined. The laser is a compact, rugged unit, completely sealed and incorporating an unheated solid catalyst. Stable operation has been successfully demonstrated over a temperature range of -35 C to 65 C.

High Repetition Rate and Frequency Stabilized Ho:YLF Laser for CO2 Differential Absorption Lidar

NASA Technical Reports Server (NTRS)

Bai, Yingxin; Yu, Jirong; Petros, M.; Petzar, Pau; Trieu, Bo; Lee, Hyung; Singh, U.

2009-01-01

High repetition rate operation of an injection seeded Ho:YLF laser has been demonstrated. For 1 kHz operation, the output pulse energy reaches 5.8mJ and the optical-to-optical efficiency is 39% when the pump power is 14.5W.

Modeling transient gain dynamics in a cladding-pumped Yb-doped fiber ampliefier pulsed at low repetition rates

NASA Technical Reports Server (NTRS)

Valley, G. C.; Wright, M.

2001-01-01

Simulations of 1-50 kHz repetition rate, pulsed Yb-fiber amplifiers show peak powers to 10 kW with half-widths < 30 ns, consistent with commercial amplifier performance. This device is a potential source for deep space-communication.

Educational Module Intervention for Radiographers to Reduce Repetition Rate of Routine Digital Chest Radiography in Makkah Region of Saudi Arabia Tertiary Hospitals: Protocol of a Quasi-Experimental Study.

PubMed

Almalki, Abdullah A; Abdul Manaf, Rosliza; Hanafiah Juni, Muhamad; Kadir Shahar, Hayati; Noor, Noramaliza Mohd; Gabbad, Abdelsafi

2017-09-26

Repetition of an image is a critical event in any radiology department. When the repetition rate of routine digital chest radiographs is high, radiation exposure of staff and patients is increased. In addition, repetition consumes the equipment's life span, thus affecting the annual budget of the department. The aim of this study is to determine the impact of a printed educational module on reducing the repetition rate of routine digital chest radiography among radiographers in Makkah Region tertiary hospitals. A quasi-experimental time series with a control group will be conducted in Makkah Region tertiary hospitals for 8 months starting in the second quarter of 2017. Four hospitals out of 5 in the region will be selected; 2 of them will be selected as the control group and the other 2 as the intervention group. Stratification and a simple random sampling technique will be used to sample 56 radiographers in each group. Pre- and postintervention assessments will be conducted to determine the radiographer knowledge, motivation, and skills and repetition rate of chest radiographs. Radiographs of the chest performed by sampled radiographers in the selected hospitals will be collected for 2 weeks before and after the intervention. A piloted questionnaire will be distributed and collected by a researcher in both groups. One-way multivariate analysis of variance and 2-way repeated multivariate analysis of variance will be used to analyze the data. It is expected that the repetition rate in the intervention group will decline after implementing the intervention and the change will be statistically significant (P<.05). Furthermore, it is expected that the knowledge, motivation, and skill levels in the intervention group will increase significantly among radiographers after implementation of the intervention (P<.05). Meanwhile, knowledge, motivation, and skills in the control group will not change. A quasi-experimental time series with a control will be conducted to investigate the effect of printed educational material in reducing the repetition rate of routine digital chest radiographs among radiographers in tertiary hospitals in the Makkah Region of Saudi Arabia. ©Abdullah A. Almalki, Rosliza Abdul Manaf, Muhamad Hanafiah Juni, Hayati Kadir Shahar, Noramaliza Mohd Noor, Abdelsafi Gabbad. Originally published in JMIR Research Protocols (http://www.researchprotocols.org), 26.09.2017.

Oral-diadochokinetic rates for Hebrew-speaking healthy ageing population: non-word versus real-word repetition.

PubMed

Ben-David, Boaz M; Icht, Michal

2017-05-01

Oral-diadochokinesis (oral-DDK) tasks are extensively used in the evaluation of motor speech abilities. Currently, validated normative data for older adults (aged 65 years and older) are missing in Hebrew. The effect of task stimuli (non-word versus real-word repetition) is also non-clear in the population of older adult Hebrew speakers. (1) To establish a norm for oral-DDK rate for older adult (aged 65 years and older) Hebrew speakers, and to investigate the possible effect of age and gender on performance rate; and (2) to examine the effects of stimuli (non-word versus real word) on oral-DDK rates. In experiment 1, 88 healthy older Hebrew speakers (60-95 years, 48 females and 40 males) were audio-recorded while performing an oral-DDK task (repetition of /pataka/), and repetition rates (syllables/s) were coded. In experiment 2, the effect of real-word repetition was evaluated. Sixty-eight older Hebrew speakers (aged 66-95 years, 43 females and 25 males) were asked to repeat 'pataka' (non-word) and 'bodeket' (Hebrew real word). Experiment 1: Oral-DDK performance for older adult Hebrew speakers was 5.07 syllables/s (SD = 1.16 syllables/s), across age groups and gender. Comparison of this data with Hebrew norms for younger adults (and equivalent data in English) shows the following gradient of oral-DDK rates: ages 15-45 > 65-74 > 75-86 years. Gender was not a significant factor in our data. Experiment 2: Repetition of real words was faster than that of non-words, by 13.5%. The paper provides normative values for oral-DDK rates for older Hebrew speakers. The data show the large impact of ageing on oro-motor functions. The analysis further indicates that speech and language pathologists should consider separate norms for clients of 65-74 years and those of 75-86 years. Hebrew rates were found to be different from English norms for the oldest group, shedding light on the impact of language on these norms. Finally, the data support using a dual-protocol (real- and non-word repetition) with older adults to improve differential diagnosis of normal and pathological ageing in this task. © 2016 Royal College of Speech and Language Therapists.

The Effects of Multiple Sets of Squats and Jump Squats on Mechanical Variables.

PubMed

Rossetti, Michael L; Munford, Shawn N; Snyder, Brandon W; Davis, Shala E; Moir, Gavin L

2017-07-28

The mechanical responses to two non-ballistic squat and two ballistic jump squat protocols performed over multiple sets were investigated. One protocol from each of the two non-ballistic and ballistic conditions incorporated a pause between the eccentric and concentric phases of the movements in order to determine the influence of the coupling time on the mechanical variables and post-activation potentiation (PAP). Eleven men (age: 21.9 ± 1.8 years; height: 1.79 ± 0.05 m; mass: 87.0 ± 7.4 kg) attended four sessions where they performed multiple sets of squats and jump squats with a load equivalent to 30% 1-repeititon maximum under one of the following conditions: 1) 3 × 4 repetitions of non-ballistic squats (30N-B); 2) 3 × 4 repetitions of non-ballistic squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PN-B); 3) 3 × 4 repetitions of ballistic jump squats (30B); 4) 3 × 4 repetitions of ballistic jump squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PB). Force plates were used to calculate variables including average vertical velocity, average vertical force (GRF), and average power output (PO). Vertical velocities during the ballistic conditions were significantly greater than those attained during the non-ballistic conditions (mean differences: 0.21 - 0.25 m/s, p<0.001, effect sizes [ES]: 1.70 - 1.89) as were GRFs (mean differences: 478 - 526 N, p<0.001, ES: 1.61 - 1.63), and PO (mean differences: 711 - 869 W, p<0.001, ES: 1.66 - 1.73). Moreover, the increase in PO across the three sets in 30B was significantly greater than the changes observed during 30N-B, 30PN-B, and 30PB (p≤0.015). The pause reduced the mechanical variables during both the non-ballistic and ballistic conditions, although the differences were not statistically significant (p>0.05). Ballistic jump squats may be an effective exercise for developing PO given the high velocities and forces generated in these exercises. Furthermore, the completion of multiple sets of jump squats may induce PAP to enhance PO. The coupling times between the eccentric and concentric phases of the jump squats should be short in order to maximize the GRF and PO across the sets.

Effect of loading on unintentional lifting velocity declines during single sets of repetitions to failure during upper and lower extremity muscle actions.

PubMed

Izquierdo, M; González-Badillo, J J; Häkkinen, K; Ibáñez, J; Kraemer, W J; Altadill, A; Eslava, J; Gorostiaga, E M

2006-09-01

The purpose of this study was to examine the effect of different loads on repetition speed during single sets of repetitions to failure in bench press and parallel squat. Thirty-six physical active men performed 1-repetition maximum in a bench press (1 RM (BP)) and half squat position (1 RM (HS)), and performed maximal power-output continuous repetition sets randomly every 10 days until failure with a submaximal load (60 %, 65 %, 70 %, and 75 % of 1RM, respectively) during bench press and parallel squat. Average velocity of each repetition was recorded by linking a rotary encoder to the end part of the bar. The values of 1 RM (BP) and 1 RM (HS) were 91 +/- 17 and 200 +/- 20 kg, respectively. The number of repetitions performed for a given percentage of 1RM was significantly higher (p < 0.001) in half squat than in bench press performance. Average repetition velocity decreased at a greater rate in bench press than in parallel squat. The significant reductions observed in the average repetition velocity (expressed as a percentage of the average velocity achieved during the initial repetition) were observed at higher percentage of the total number of repetitions performed in parallel squat (48 - 69 %) than in bench press (34 - 40 %) actions. The major finding in this study was that, for a given muscle action (bench press or parallel squat), the pattern of reduction in the relative average velocity achieved during each repetition and the relative number of repetitions performed was the same for all percentages of 1RM tested. However, relative average velocity decreased at a greater rate in bench press than in parallel squat performance. This would indicate that in bench press the significant reductions observed in the average repetition velocity occurred when the number of repetitions was over one third (34 %) of the total number of repetitions performed, whereas in parallel squat it was nearly one half (48 %). Conceptually, this would indicate that for a given exercise (bench press or squat) and percentage of maximal dynamic strength (1RM), the pattern of velocity decrease can be predicted over a set of repetitions, so that a minimum repetition threshold to ensure maximal speed performance is determined.

Upper arm elevation and repetitive shoulder movements: a general population job exposure matrix based on expert ratings and technical measurements.

PubMed

Dalbøge, Annett; Hansson, Gert-Åke; Frost, Poul; Andersen, Johan Hviid; Heilskov-Hansen, Thomas; Svendsen, Susanne Wulff

2016-08-01

We recently constructed a general population job exposure matrix (JEM), The Shoulder JEM, based on expert ratings. The overall aim of this study was to convert expert-rated job exposures for upper arm elevation and repetitive shoulder movements to measurement scales. The Shoulder JEM covers all Danish occupational titles, divided into 172 job groups. For 36 of these job groups, we obtained technical measurements (inclinometry) of upper arm elevation and repetitive shoulder movements. To validate the expert-rated job exposures against the measured job exposures, we used Spearman rank correlations and the explained variance[Formula: see text] according to linear regression analyses (36 job groups). We used the linear regression equations to convert the expert-rated job exposures for all 172 job groups into predicted measured job exposures. Bland-Altman analyses were used to assess the agreement between the predicted and measured job exposures. The Spearman rank correlations were 0.63 for upper arm elevation and 0.64 for repetitive shoulder movements. The expert-rated job exposures explained 64% and 41% of the variance of the measured job exposures, respectively. The corresponding calibration equations were y=0.5%time+0.16×expert rating and y=27°/s+0.47×expert rating. The mean differences between predicted and measured job exposures were zero due to calibration; the 95% limits of agreement were ±2.9% time for upper arm elevation >90° and ±33°/s for repetitive shoulder movements. The updated Shoulder JEM can be used to present exposure-response relationships on measurement scales. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Indicators of Student Flow Rates in Honduras: An Assessment of an Alternative Methodology, with Two Methodologies for Estimating Student Flow Rates. BRIDGES Research Report No. 6.

ERIC Educational Resources Information Center

Cuadra, Ernesto; Crouch, Luis

Student promotion, repetition, and dropout rates constitute the basic data needed to forecast future enrollment and new resources. Information on student flow is significantly related to policy formulation aimed at improving internal efficiency, because dropping out and grade repetition increase per pupil cost, block access to eligible school-age…

Grade Repetition in Queensland State Prep Classes

ERIC Educational Resources Information Center

Anderson, Robyn

2012-01-01

The current study considers grade repetition rates in the early years of schooling in Queensland state schools with specific focus on the pre-schooling year, Prep. In particular, it provides empirical evidence of grade repetition in Queensland state schools along with groups of students who are more often repeated. At the same time, much of the…

Task Repetition and Second Language Speech Processing

ERIC Educational Resources Information Center

Lambert, Craig; Kormos, Judit; Minn, Danny

2017-01-01

This study examines the relationship between the repetition of oral monologue tasks and immediate gains in L2 fluency. It considers the effect of aural-oral task repetition on speech rate, frequency of clause-final and midclause filled pauses, and overt self-repairs across different task types and proficiency levels and relates these findings to…

77 FR 31814 - National Flood Insurance Program (NFIP); Insurance Coverage and Rates

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-30

... structures (target repetitive loss buildings) insured under the NFIP. The Notice of Proposed Rulemaking (NPRM) defined target repetitive loss buildings as those with four or more losses, or with two or more flood... flood insurance coverage to a target repetitive loss building, if an owner declined an offer of...

A flexible master oscillator for a pulse-burst laser system

NASA Astrophysics Data System (ADS)

Den Hartog, D. J.; Young, W. C.

2015-12-01

A new master oscillator is being installed in the pulse-burst laser system used for high-rep-rate Thomson scattering on the MST experiment. This new master oscillator will enable pulse repetition rates up to 1 MHz, with the ability to program a burst of pulses with arbitrary and varying time separation between each pulse. In addition, the energy of each master oscillator pulse can be adjusted to compensate for gain variations in the power amplifier section of the laser system. This flexibility is accomplished by chopping a CW laser source with a high-bandwidth acousto-optic modulator (AOM). The laser source is a Laser Quantum ventus 1064 diode-pumped solid-state laser with continuous output power variable from 100 to 500 mW. The 1064 nm, 2.7 mm diameter polarized beam is focused into the gallium phosphide crystal of a Brimrose AOM, which deflects the beam by approximately 60 mR when driven by the 400 MHz fixed frequency driver. Beam deflection is controlled by a simple digital input pulse, and is capable of producing deflected pulses of less than 20 ns width at repetition rates much greater than 1 MHz. These deflected pulses from the output of the AOM are collimated and propagated into the laser amplifier system, where they will be amplified to ~ 2 J/pulse and injected into the MST plasma.

Supported treadmill ambulation for amyotrophic lateral sclerosis: a pilot study.

PubMed

Sanjak, Mohammed; Bravver, Elena; Bockenek, William L; Norton, H James; Brooks, Benjamin R

2010-12-01

To determine the feasibility, tolerability, safety, and exercise treatment-effect size of repetitive rhythmic exercise mediated by supported treadmill ambulation training (STAT) for patients with amyotrophic lateral sclerosis (ALS). Interventional with repeated-measures design. Multidisciplinary ALS clinic at academic medical center. Convenience sample of patients with ALS (N=9) who were ambulatory with assistive devices (Sinaki-Mulder stages II-III). Repetitive rhythmic exercise-STAT (30min total; 5min of exercise intercalated with 5min of rest) performed 3 times a week for 8 weeks. ALS Functional Rating Scale-Revised (ALSFRS-R), percentage of predicted vital capacity (VC), total lower-extremities manual muscle test (MMT), rate of perceived exertion (RPE), Fatigue Severity Scale (FSS), and maximum voluntary isometric contraction (MVIC) in 10 lower and 10 upper extremities. Gait performance, which included walking distance, speed, steps, and stride length, was evaluated during treadmill and ground 6-minute walk tests (6MWTs) and 25-foot walk test (25FWT). Feasibility issues decreased screened participants by 4 patients (31%). Nine patients were enrolled, but 6 patients (67%) completed the study and 3 (23% of original cohort; 33% of enrolled cohort) could not complete the exercise intervention because of non-ALS-related medical problems. Tolerability of the intervention measures during the treadmill 6MWT showed improvement in RPE (P≤.05) and FSS score (P≥.05). Safety measures (ALSFRS-R, VC, MMT) showed no decrease and showed statistical improvement in ALSFRS-R score (P≤.05) during the study interval. Exercise treatment-effect size showed variable improvements. Gait speed, distance, and stride length during the treadmill 6MWT improved significantly (P≤.05) after 4 weeks and improvements were maintained after 8 weeks compared with baseline. Walking distance during the ground 6MWT increased significantly after 4 weeks and was maintained after 8 weeks compared with baseline (P≤.05). Walking speed during the 25FWT and lower-extremity MVIC improved, but were not statistically significant. Repetitive rhythmic exercise-STAT is feasible, tolerated, and safe for patients with ALS. Repetitive rhythmic exercise-STAT treatment-effect size across a number of ALS-related measures was consistent with improved work capacity and gait function in patients with ALS who are dependent on assistive devices for ambulation. Repetitive rhythmic exercise-STAT should be evaluated further in larger studies to determine the stability of this improved function in relation to the rate of progression of the underlying ALS. Copyright © 2010 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Interaction of Repetitively Pulsed High Energy Laser Radiation With Matter

NASA Astrophysics Data System (ADS)

Hugenschmidt, Manfred

1986-10-01

The paper is concerned with laser target interaction processes involving new methods of improving the overall energy balance. As expected theoretically, this can be achieved with high repetition rate pulsed lasers even for initially highly reflecting materials, such as metals. Experiments were performed by using a pulsed CO2 laser at mean powers up to 2 kW and repetition rates up to 100 Hz. The rates of temperature rise of aluminium for example were thereby increased by lore than a factor of 3 as compared to cw-radiation of comparable power density. Similar improvements were found for the overall absorptivities that were increased by this method by more than an order of magnitude.

High power high repetition rate diode side-pumped Q-switched Nd:YAG rod laser

NASA Astrophysics Data System (ADS)

Lebiush, E.; Lavi, R.; Tzuk, Y.; Jackel, S.; Lallouz, R.; Tsadka, S.

1998-01-01

A Q-switched diode side-pumped Nd:YAG rod laser is presented. The design is based on close coupled diodes which are mounted side by side to a laser rod cut at Brewster angle. No intra-cavity optics are needed to compensate for the induced thermal lensing of the rod. This laser produces 10 W average power with 30 ns pulse width and beam quality of 1.3 times diffraction limited at 10 kHz repetition rate. The light to light conversion efficiency is 12%. The same average power and beam quality is kept while operating the laser at repetition rates up to 50 kHz.

High-average-power 2 μm few-cycle optical parametric chirped pulse amplifier at 100 kHz repetition rate.

PubMed

Shamir, Yariv; Rothhardt, Jan; Hädrich, Steffen; Demmler, Stefan; Tschernajew, Maxim; Limpert, Jens; Tünnermann, Andreas

2015-12-01

Sources of long wavelengths few-cycle high repetition rate pulses are becoming increasingly important for a plethora of applications, e.g., in high-field physics. Here, we report on the realization of a tunable optical parametric chirped pulse amplifier at 100 kHz repetition rate. At a central wavelength of 2 μm, the system delivered 33 fs pulses and a 6 W average power corresponding to 60 μJ pulse energy with gigawatt-level peak powers. Idler absorption and its crystal heating is experimentally investigated for a BBO. Strategies for further power scaling to several tens of watts of average power are discussed.

Generation of tunable, high repetition rate optical frequency combs using on-chip silicon modulators

NASA Astrophysics Data System (ADS)

Nagarjun, K. P.; Jeyaselvan, Vadivukarassi; Selvaraja, Shankar Kumar; Supradeepa, V. R.

2018-04-01

We experimentally demonstrate tunable, highly-stable frequency combs with high repetition-rates using a single, charge injection based silicon PN modulator. In this work, we demonstrate combs in the C-band with over 8 lines in a 20-dB bandwidth. We demonstrate continuous tuning of the center frequency in the C-band and tuning of the repetition-rate from 7.5GHz to 12.5GHz. We also demonstrate through simulations the potential for bandwidth scaling using an optimized silicon PIN modulator. We find that, the time varying free carrier absorption due to carrier injection, an undesirable effect in data modulators, assists here in enhancing flatness in the generated combs.

Function word repetitions emerge when speakers are operantly conditioned to reduce frequency of silent pauses.

PubMed

Howell, P; Sackin, S

2001-09-01

Beattie and Bradbury (1979) reported a study in which, in one condition, they punished speakers when they produced silent pauses (by lighting a light they were supposed to keep switched off). They found speakers were able to reduce silent pauses and that this was not achieved at the expense of reduced overall speech rate. They reported an unexpected increase in word repetition rate. A recent theory proposed by Howell, Au-Yeung, and Sackin (1999) predicts that the change in word repetition rate will occur on function, not content words. This hypothesis is tested and confirmed. The results are used to assess the theory and to consider practical applications of this conditioning procedure.

2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

NASA Technical Reports Server (NTRS)

Singh, Upendra N.; Bai, Yingxin; Yu, Jirong

2009-01-01

Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed in NASA Langley Research Center. This laser system is capable of making a vertical profiling of CO2 from ground and column measurement of CO2 from air and space-borne platform. The transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. A Ho:YLF laser operating in the range of 2.05 micrometers can be tuned over several characteristic lines of CO2 absorption. Experimentally, a diode pumped Ho:Tm:YLF laser has been successfully used as the transmitter of coherent differential absorption lidar for the measurement of CO2 with a repetition rate of 5 Hz and pulse energy of 75 mJ. For coherent detection, high repetition rate is required for speckle averaging to obtain highly precise measurements. However, a diode pumped Ho:Tm:YLF laser can not operate in high repetition rate due to the large heat loading and up-conversion. A Tm:fiber laser pumped Ho:YLF laser with low heat loading can operate in high repetition rate. A theoretical model has been established to simulate the performance of Tm:fiber laser pumped Ho:YLF lasers. For continuous wave (CW) operation, high pump intensity with small beam size is suitable for high efficiency. For Q-switched operation, the optimal energy extraction relies on the pump intensity, pump volume, and pump duration which is inversely proportion to the repetition rate. CW and Q-switched Ho:YLF lasers with different linear cavity configurations have been designed and demonstrated for a 30 W Tm:fiber pump laser. The CW Ho laser slope efficiency and optical-to-optical efficiencies reach 65% and 55%, respectively. The pulsed laser efficiency depends on the repetition rate. For 1 kHz operation, the optical-to-optical efficiency is 39% when the pump power is 14.5W. Currently, the injection seeding success rate is between 99.4% and 99.95%. After a ten thousand pulses, the standard deviation of the laser frequency jitter is about 3 MHz. It meets the requirements of highly precise CO2 concentration measurement. In conclusion, an injection seeded, high repetition rate, Q-switched Ho:YLF laser has been developed for a coherent CO2 differential absorption lidar. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. It can potentially meet the requirements of the coherent detection of CO2 concentration by a differential absorption lidar technique.

Exercise Variability: A Prescription for Overuse Injury Prevention.

ERIC Educational Resources Information Center

Dufek, Janet S.

2002-01-01

Overuse injuries result from repetitive microtrauma to the body. This paper introduces the concept of performance variability and expands the concept to an attitude of exercise variability, which may be helpful in avoiding overuse injuries. It explains what to watch out for with overuse injuries and presents suggestions for avoiding overuse…

Pulsed Power Design for a Small Repetitively Pulsed Electron Beam Pumped KrF Laser

DTIC Science & Technology

2003-06-01

fusion energy (IFE) requirements for rep-rate, efficiency, durability and cost. We have designed a pulsed power system for the pre-amplifier in the Electra...new advanced pulsed power topology that can meet the fusion energy requirements for durability, repetition rate, and cost. The pulsed power will first

Efficient high repetition rate electro-optic Q-switched laser with an optically active langasite crystal

PubMed Central

Ma, Shihui; Yu, Haohai; Zhang, Huaijin; Han, Xuekun; Lu, Qingming; Ma, Changqin; Boughton, Robert I.; Wang, Jiyang

2016-01-01

With an optically active langasite (LGS) crystal as the electro-optic Q-switch, we demonstrate an efficient Q-switched laser with a repetition rate of 200 kHz. Based on the theoretical analysis of the interaction between optical activity and electro-optic property, the optical activity of the crystal has no influence on the birefringence during Q-switching if the quarter wave plate used was rotated to align with the polarization direction. With a Nd:LuVO4 crystal possessing a large emission cross-section and a short fluorescence lifetime as the gain medium, a stable LGS Q-switched laser was designed with average output power of 4.39 W, corresponding to a slope efficiency of 29.4% and with a minimum pulse width of 5.1 ns. This work represents the highest repetition rate achieved so far in a LGS Q-switched laser and it can provide a practical Q-switched laser with a tunable high repetition rates for many applications, such as materials processing, laser ranging, medicine, military applications, biomacromolecule materials, remote sensing, etc. PMID:27461819

Performance of large aperture tapered fiber phase conjugate mirror with high pulse energy and 1-kHz repetition rate.

PubMed

Zhao, Zhigang; Dong, Yantao; Pan, Sunqiang; Liu, Chong; Chen, Jun; Tong, Lixin; Gao, Qingsong; Tang, Chun

2012-01-16

A large aperture fused silica tapered fiber phase conjugate mirror is presented with a maximum 70% stimulated Brillouin scattering (SBS) reflectivity, which is obtained with 1 kHz repetition rate, 15 ns pulse width and 38 mJ input pulse energy. To the best of our knowledge, this is the highest SBS reflectivity ever reported by using optical fiber as a phase conjugate mirror for such high pulse repetition rate (1 kHz) and several tens of millijoule (mJ) input pulse energy. The influences of fiber end surface quality and pump pulse widths on SBS reflectivity are investigated experimentally. The results show that finer fiber end surface quality and longer input pulse widths are preferred for obtaining higher SBS reflectivity with higher input pulse energy. Double passing amplification experiments are also performed. 52 mJ pulse energy is achieved at 1 kHz repetition rate, with a reflected SBS pulse width of 1.5 ns and a M(2) factor of 2.3. The corresponding peak power reaches 34.6 MW. Obvious beam quality improvement is observed.

Highly efficient, versatile, self-Q-switched, high-repetition-rate microchip laser generating Ince-Gaussian modes for optical trapping

NASA Astrophysics Data System (ADS)

Dong, Jun; He, Yu; Zhou, Xiao; Bai, Shengchuang

2016-03-01

Lasers operating in the Ince-Gaussian (IG) mode have potential applications for optical manipulation of microparticles and formation of optical vortices, as well as for optical trapping and optical tweezers. Versatile, self-Q-switched, high-peak-power, high-repetition-rate Cr, Nd:YAG microchip lasers operating in the IG mode are implemented under tilted, tightly focused laser-diode pumping. An average output power of over 2 W is obtained at an absorbed pump power of 6.4 W. The highest optical-to-optical efficiency of 33.2% is achieved at an absorbed pump power of 3.9 W. Laser pulses with a pulse energy of 7.5 μJ, pulse width of 3.5 ns and peak power of over 2 kW are obtained. A repetition rate up to 335 kHz is reached at an absorbed pump power of 5.8 W. Highly efficient, versatile, IG-mode lasers with a high repetition rate and a high peak power ensure a better flexibility in particle manipulation and optical trapping.

Highly efficient, versatile, self-Q-switched, high-repetition-rate microchip laser generating Ince–Gaussian modes for optical trapping

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

Jun Dong; Yu He; Xiao Zhou

2016-03-31

Lasers operating in the Ince-Gaussian (IG) mode have potential applications for optical manipulation of microparticles and formation of optical vortices, as well as for optical trapping and optical tweezers. Versatile, self-Q-switched, high-peak-power, high-repetition-rate Cr, Nd:YAG microchip lasers operating in the IG mode are implemented under tilted, tightly focused laser-diode pumping. An average output power of over 2 W is obtained at an absorbed pump power of 6.4 W. The highest optical-to-optical efficiency of 33.2% is achieved at an absorbed pump power of 3.9 W. Laser pulses with a pulse energy of 7.5 μJ, pulse width of 3.5 ns and peakmore » power of over 2 kW are obtained. A repetition rate up to 335 kHz is reached at an absorbed pump power of 5.8 W. Highly efficient, versatile, IG-mode lasers with a high repetition rate and a high peak power ensure a better flexibility in particle manipulation and optical trapping. (control of laser radiation parameters)« less

MeV proton acceleration at kHz repetition rate from ultra-intense laser liquid interaction

NASA Astrophysics Data System (ADS)

Morrison, John T.; Feister, Scott; Frische, Kyle D.; Austin, Drake R.; Ngirmang, Gregory K.; Murphy, Neil R.; Orban, Chris; Chowdhury, Enam A.; Roquemore, W. M.

2018-02-01

Laser acceleration of ions to ≳MeV energies has been achieved on a variety of Petawatt laser systems, raising the prospect of ion beam applications using compact ultra-intense laser technology. However, translation from proof-of-concept laser experiment into real-world application requires MeV-scale ion energies and an appreciable repetition rate (>Hz). We demonstrate, for the first time, proton acceleration up to 2 MeV energies at a kHz repetition rate using a milli-joule-class short-pulse laser system. In these experiments, 5 mJ of ultrashort-pulse laser energy is delivered at an intensity near 5× {10}18 {{W}} {cm}}-2 onto a thin-sheet, liquid-density target. Key to this effort is a flowing liquid ethylene glycol target formed in vacuum with thicknesses down to 400 nm and full recovery at 70 μs, suggesting its potential use at ≫kHz rate. Novel detectors and experimental methods tailored to high-repetition-rate ion acceleration by lasers were essential to this study and are described. In addition, particle-in-cell simulations of the laser-plasma interaction show good agreement with experimental observations.

Differentiating youth who are bullied from other victims of peer-aggression: the importance of differential power and repetition

PubMed Central

Ybarra, Michele L.; Espelage, Dorothy L.; Mitchell, Kimberly J.

2014-01-01

Purpose Examine whether: 1) among youth who report being bullied, differential power and repetition are useful in identifying youth who are more or less affected by the victimization experience; and 2) bullying and more generalized peer aggression are distinct or overlapping constructs. Methods Data for the Teen Health and Technology (THT) study were collected online between August 2010 and January 2011 from 3,989 13–18 year olds. Data from the Growing up with Media (GuwM) study (Wave 3) were collected online in 2008 from 1,157 12–17 year olds. Results In the THT study, youth who reported neither differential power nor repetition had the lowest rates of interference with daily functioning. Youth who reported either differential power or repetition had higher rates; but the highest rates of interference with daily functioning were observed among youth who reported both differential power and repetition. In the GuwM study, youth were victims of online generalized peer aggression (30%) or both online generalized peer aggression and cyberbullying (16%), but rarely cyberbullying alone (1%). Conclusions Both differential power and repetition are key in identifying youth who are bullied and at particular risk for concurrent psychosocial challenge. Each feature needs to be measured directly. Generalized peer aggression appears to be a broader form of violence compared to bullying. It needs to be recognized that youth who are victimized but do not meet the criteria of bullying have elevated rates of problems. They are an important, albeit non-bullied, group of victimized youth to be included in research. PMID:24726463

Effects of repetitive pulsing on multi-kHz planar laser-induced incandescence imaging in laminar and turbulent flames

DOE PAGES

Michael, James B.; Venkateswaran, Prabhakar; Shaddix, Christopher R.; ...

2015-04-08

Planar laser-induced incandescence (LII) imaging is reported at repetition rates up to 100 kHz using a burst-mode laser system to enable studies of soot formation dynamics in highly turbulent flames. Furthermore, to quantify the accuracy and uncertainty of relative soot volume fraction measurements, the temporal evolution of the LII field in laminar and turbulent flames is examined at various laser operating conditions. Under high-speed repetitive probing, it is found that LII signals are sensitive to changes in soot physical characteristics when operating at high laser fluences within the soot vaporization regime. For these laser conditions, strong planar LII signals aremore » observed at measurement rates up to 100 kHz but are primarily useful for qualitative tracking of soot structure dynamics. However, LII signals collected at lower fluences allow sequential planar measurements of the relative soot volume fraction with a sufficient signal-to-noise ratio at repetition rates of 10–50 kHz. Finally, guidelines for identifying and avoiding the onset of repetitive probe effects in the LII signals are discussed, along with other potential sources of measurement error and uncertainty.« less

Phase-stable, multi-µJ femtosecond pulses from a repetition-rate tunable Ti:Sa-oscillator-seeded Yb-fiber amplifier

NASA Astrophysics Data System (ADS)

Saule, T.; Holzberger, S.; De Vries, O.; Plötner, M.; Limpert, J.; Tünnermann, A.; Pupeza, I.

2017-01-01

We present a high-power, MHz-repetition-rate, phase-stable femtosecond laser system based on a phase-stabilized Ti:Sa oscillator and a multi-stage Yb-fiber chirped-pulse power amplifier. A 10-nm band around 1030 nm is split from the 7-fs oscillator output and serves as the seed for subsequent amplification by 54 dB to 80 W of average power. The µJ-level output is spectrally broadened in a solid-core fiber and compressed to 30 fs with chirped mirrors. A pulse picker prior to power amplification allows for decreasing the repetition rate from 74 MHz by a factor of up to 4 without affecting the pulse parameters. To compensate for phase jitter added by the amplifier to the feed-forward phase-stabilized seeding pulses, a self-referencing feed-back loop is implemented at the system output. An integrated out-of-loop phase noise of less than 100 mrad was measured in the band from 0.4 Hz to 400 kHz, which to the best of our knowledge corresponds to the highest phase stability ever demonstrated for high-power, multi-MHz-repetition-rate ultrafast lasers. This system will enable experiments in attosecond physics at unprecedented repetition rates, it offers ideal prerequisites for the generation and field-resolved electro-optical sampling of high-power, broadband infrared pulses, and it is suitable for phase-stable white light generation.

A linear accelerator for simulated micrometeors.

NASA Technical Reports Server (NTRS)

Slattery, J. C.; Becker, D. G.; Hamermesh, B.; Roy, N. L.

1973-01-01

Review of the theory, design parameters, and construction details of a linear accelerator designed to impart meteoric velocities to charged microparticles in the 1- to 10-micron diameter range. The described linac is of the Sloan Lawrence type and, in a significant departure from conventional accelerator practice, is adapted to single particle operation by employing a square wave driving voltage with the frequency automatically adjusted from 12.5 to 125 kHz according to the variable velocity of each injected particle. Any output velocity up to about 30 km/sec can easily be selected, with a repetition rate of approximately two particles per minute.

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

Karr, T.J.

The SAR energy-aperture product limit is extended to multi-beam SARS, Spotlight and moving spotlight SARS. This fundamental limit bounds the tradeoff between energy and antenna size. The kinematic relations between design variables such as platform speed, pulse repetition frequency, beam width and area rate are analyzed in a unified framework applicable to a wide variety of SARs including strip maps, spotlights, vermer arrays and multi-beam SARS, both scanning and swept-beam. Then the energy-aperture product limit is derived from the signal-to noise requirement and the kinematic constraints. The derivation clarifies impact of multiple beams and spotlighting on SAR performance.

Velocity Loss as a Variable for Monitoring Resistance Exercise.

PubMed

González-Badillo, Juan José; Yañez-García, Juan Manuel; Mora-Custodio, Ricardo; Rodríguez-Rosell, David

2017-03-01

This study aimed to analyze: 1) the pattern of repetition velocity decline during a single set to failure against different submaximal loads (50-85% 1RM) in the bench press exercise; and 2) the reliability of the percentage of performed repetitions, with respect to the maximum possible number that can be completed, when different magnitudes of velocity loss have been reached within each set. Twenty-two men performed 8 tests of maximum number of repetitions (MNR) against loads of 50-55-60-65-70-75-80-85% 1RM, in random order, every 6-7 days. Another 28 men performed 2 separate MNR tests against 60% 1RM. A very close relationship was found between the relative loss of velocity in a set and the percentage of performed repetitions. This relationship was very similar for all loads, but particularly for 50-70% 1RM, even though the number of repetitions completed at each load was significantly different. Moreover, the percentage of performed repetitions for a given velocity loss showed a high absolute reliability. Equations to predict the percentage of performed repetitions from relative velocity loss are provided. By monitoring repetition velocity and using these equations, one can estimate, with considerable precision, how many repetitions are left in reserve in a bench press exercise set. © Georg Thieme Verlag KG Stuttgart · New York.

Neural Repetition Effects in the Medial Temporal Lobe Complex are Modulated by Previous Encoding Experience

PubMed Central

Greene, Ciara M.; Soto, David

2012-01-01

It remains an intriguing question why the medial temporal lobe (MTL) can display either attenuation or enhancement of neural activity following repetition of previously studied items. To isolate the role of encoding experience itself, we assessed neural repetition effects in the absence of any ongoing task demand or intentional orientation to retrieve. Experiment 1 showed that the hippocampus and surrounding MTL regions displayed neural repetition suppression (RS) upon repetition of past items that were merely attended during an earlier study phase but this was not the case following re-occurrence of items that had been encoded into working memory (WM). In this latter case a trend toward neural repetition enhancement (RE) was observed, though this was highly variable across individuals. Interestingly, participants with a higher degree of neural RE in the MTL complex displayed higher memory sensitivity in a later, surprise recognition test. Experiment 2 showed that massive exposure at encoding effected a change in the neural architecture supporting incidental repetition effects, with regions of the posterior parietal and ventral-frontal cortex in addition to the hippocampus displaying neural RE, while no neural RS was observed. The nature of encoding experience therefore modulates the expression of neural repetition effects in the MTL and the neocortex in the absence of memory goals. PMID:22829892

A fiber-based quasi-continuous-wave quantum key distribution system

PubMed Central

Shen, Yong; Chen, Yan; Zou, Hongxin; Yuan, Jianmin

2014-01-01

We report a fiber-based quasi-continuous-wave (CW) quantum key distribution (QKD) system with continuous variables (CV). This system employs coherent light pulses and time multiplexing to maximally reduce cross talk in the fiber. No-switching detection scheme is adopted to optimize the repetition rate. Information is encoded on the sideband of the pulsed coherent light to fully exploit the continuous wave nature of laser field. With this configuration, high secret key rate can be achieved. For the 50 MHz detected bandwidth in our experiment, when the multidimensional reconciliation protocol is applied, a secret key rate of 187 kb/s can be achieved over 50 km of optical fiber against collective attacks, which have been shown to be asymptotically optimal. Moreover, recently studied loopholes have been fixed in our system. PMID:24691409

308-nm excimer laser ablation of human cartilage

NASA Astrophysics Data System (ADS)

Prodoehl, John A.; Rhodes, Anthony L.; Meller, Menachem M.; Sherk, Henry H.

1993-07-01

The XeCl excimer laser was investigated as an ablating tool for human fibrocartilage and hyaline cartilage. Quantitative measurements were made of tissue ablation rates as a function of fluence in meniscal fibrocartilage and articular hyaline cartilage. A force of 1.47 Newtons was applied to an 800 micrometers fiber with the laser delivering a range of fluences (40 to 190 mj/mm2) firing at a frequency of 5 Hz. To assess the effect of repetition rate on ablation rate, a set of measurements was made at a constant fluence of 60 mj/mm2, with the repetition rate varying from 10 to 40 Hz. Histologic and morphometric analysis was performed using light microscopy. The results of these studies revealed that the ablation rate was directly proportional to fluence over the range tested. Fibrocartilage was ablated at a rate 2.56 times faster than hyaline cartilage at the maximum fluence tested. Repetition rate had no effect on the penetration per pulse. Adjacent tissue damage was noted to be minimal (10 - 70 micrometers ).

Quality and Quantity of Rehabilitation Exercises Delivered By A 3-D Motion Controlled Camera: A Pilot Study.

PubMed

Komatireddy, Ravi; Chokshi, Anang; Basnett, Jeanna; Casale, Michael; Goble, Daniel; Shubert, Tiffany

2014-08-01

Tele-rehabiliation technologies that track human motion could enable physical therapy in the home. To be effective, these systems need to collect critical metrics without PT supervision both in real time and in a store and forward capacity. The first step of this process is to determine if PTs (PTs) are able to accurately assess the quality and quantity of an exercise repetition captured by a tele-rehabilitation platform. The purpose of this pilot project was to determine the level of agreement of quality and quantity of an exercise delivered and assessed by the Virtual Exercise Rehabilitation Assistant (VERA), and seven PTs. Ten healthy subjects were instructed by a PT in how to perform four lower extremity exercises. Subjects then performed each exercises delivered by VERA which counted repetitions and quality. Seven PTs independently reviewed video of each subject's session and assessed repetitions quality. The percent difference in total repetitions and analysis of the distribution of rating repetition quality was assessed between the VERA and PTs. The VERA counted 426 repetitions across 10 subjects performing the four different exercises while the mean repetition count from the PT panel was 426.7 (SD = 0.8). The VERA underestimated the total repetitions performed by 0.16% (SD = 0.03%, 95% CI 0.12 - 0. 22). Chi square analysis across raters was χ 2 = 63.17 (df = 6, p<.001), suggesting significant variance in at least one rater. The VERA count of repetitions was accurate in comparison to a seven member panel of PTs. For exercise quality the VERA was able to rate 426 exercise repetitions across 10 patients and four different exercises in a manner consistent with five out of seven experienced PTs.

Oral-diadochokinetic rates for Hebrew-speaking school-age children: real words vs. non-words repetition.

PubMed

Icht, Michal; Ben-David, Boaz M

2015-02-01

Oral-diadochokinesis (DDK) tasks are a common tool for evaluating speech disorders. Usually, these tasks involve repetitions of non-words. It has been suggested that repeating real words can be more suitable for preschool children. But, the impact of using real words with elementary school children has not been studied yet. This study evaluated oral-DDK rates for Hebrew-speaking elementary school children using non-words and real words. The participants were 60 children, 9-11 years old, with normal speech and language development, who were asked to repeat "pataka" (non-word) and "bodeket" (Hebrew real word). Data replicate the advantage generally found for real word repetition with preschoolers. Children produced real words faster than non-words for all age groups, and repetition rates were higher for the older children. The findings suggest that adding real words to the standard oral-DDK task with elementary school children may provide a more comprehensive picture of oro-motor function.

Neodymium glass laser with a phase conjugate mirror producing 220 J pulses at 0.02 Hz repetition rate.

PubMed

Kuzmin, A A; Khazanov, E A; Kulagin, O V; Shaykin, A A

2014-08-25

For pumping multipetawatt Ti:sapphire laser facilities we developed a compact repetitively pulsed laser based on neodymium phosphate glass with pulse energy of 220 J, pulse repetition rate of 0.02 Hz, beam diameter of 43 mm, aperture fill factor of 0.8, and FWHM pulse duration of 30 ns. The phase distortions of laser radiation were compensated by optical phase conjugation via stimulated Brillouin scattering. The depolarization was reduced to 0.4% using linear compensation methods. The beam quality was 2.5 x diffraction limit (150 µrad).

The contribution of volume, technique, and load to single-repetition and total-repetition kinematics and kinetics in response to three loading schemes.

PubMed

Crewther, Blair T; Cronin, John; Keogh, Justin W L

2008-11-01

This study examined the effect of volume, technique, and load upon single-repetition and total-repetition kinematics and kinetics during three loading schemes. Eleven recreationally trained males each performed a power (8 sets of 6 repetitions at 45% of one-repetition maximum [1RM], 3-minute rest periods, explosive and ballistic movements), hypertrophy (10 sets of 10 repetitions at 75% 1RM, 2-minute rest periods, controlled movements), and maximal strength (6 sets of 4 repetitions at 88% 1RM, 4-minute rest periods, explosive intent) scheme involving squats. Examination of repetition data showed that load intensity (% 1RM) generally had a direct effect on forces, contraction times, impulses, and work (i.e., increasing with load), whereas power varied across loads (p < 0.001). However, total-repetition forces, contraction times, impulses, work, and power were all greater in the hypertrophy scheme (p < 0.001), because of the greater number of repetitions performed (volume) as well as lifting technique. No differences in total forces were found between the equal-volume power and maximal strength schemes, but the former did produce greater total contraction times, work, and power (p < 0.001), which may also be attributed to repetition and technique differences. Total impulses were the only variable greater in the maximal strength scheme (p < 0.001). Thus, the interaction of load, volume, and technique plays an important role in determining the mechanical responses (stimuli) afforded by these workouts. These findings may explain disparities cited within research, regarding the effectiveness of different loading strategies for hypertrophy, maximal strength, and power adaptation.

[Analysis of fragments of intergenome spacers of human body observed in chromosomes containing no nuclear organization].

PubMed

Kupriyanova, N S; Nechvolodov, K K; Korsunenko, A V

2014-01-01

Tandem repetitions of rDNA provide so-called nuclear organizations (NOR). On the other hand, rDNA-structures are observed in some NOR chromosomes. It was demonstrated that, in addition to ribosome biogenesis, nucleoli provided a number of functions: cell cycle regulation, stress-induced response, transcription regulation, which often induced cell cascades. The mechanisms of the induction of rDNA segments in NOR chromosomes are obscure and require further research. About 1/3 repetitions are associated with nucleoli and SINE/Alu repetitions, homogeneous repetition, and tandem repetition. Perhaps, relative position of nucleoli and chromosomes may facilitate/prevent interaction of chromosomes with rDNA clusters. The variability of two larger repetitions in the central part of rMGS, LR1, and LR2 similar by -90% and separated by several hundred pairs of bases from each other was studied in our previous works. This work was devoted to the search for the LR1-LR2 segments in other chromosomes, characterization of their terminal tips at rupture points and genome areas of incorporation of the LR1-LR2 segments.

Estimation of Promotion, Repetition and Dropout Rates for Learners in South African Schools

ERIC Educational Resources Information Center

Uys, Daniël Wilhelm; Alant, Edward John Thomas

2015-01-01

A new procedure for estimating promotion, repetition and dropout rates for learners in South African schools is proposed. The procedure uses three different data sources: data from the South African General Household survey, data from the Education Management Information Systems, and data from yearly reports published by the Department of Basic…

Function Word Repetitions Emerge When Speakers Are Operantly Conditioned to Reduce Frequency of Silent Pauses

PubMed Central

Howell, Peter; Sackin, Stevie

2007-01-01

Beattie and Bradbury (1979) reported a study in which, in one condition, they punished speakers when they produced silent pauses (by lighting a light they were supposed to keep switched off). They found speakers were able to reduce silent pauses and that this was not achieved at the expense of reduced overall speech rate. They reported an unexpected increase in word repetition rate. A recent theory proposed by Howell, Au-Yeung, and Sackin (1999) predicts that the change in word repetition rate will occur on function, not content words. This hypothesis is tested and confirmed. The results are used to assess the theory and to consider practical applications of this conditioning procedure. PMID:11529422

Graphene oxide based reflective saturable absorber for Q-switched and mode-locked YVO4/Nd:YVO4/YVO4 laser

NASA Astrophysics Data System (ADS)

Zhang, Gang; Wang, Yonggang; Chen, Zhendong; Jiao, Zhiyong

2018-05-01

A reflective graphene oxide saturable absorber is fabricated and used in a Q-switched and mode-locked YVO4/Nd:YVO4/YVO4 laser. Stable Q-switched and mode-locked pulses with a repetition rate of 8 MHz can be obtained at a pump power of 9 W by using an X-type resonator. Pulses obtained in an X-type resonator possess higher stability, output power, and repetition rate, compared with those in a Z-type resonator. The pulse width and the repetition rate of the Q-switched envelop in an X-type resonator are superior to those in the reported Q-switched and mode-locked lasers with graphene oxide.

A simple sub-nanosecond ultraviolet light pulse generator with high repetition rate and peak power.

PubMed

Binh, P H; Trong, V D; Renucci, P; Marie, X

2013-08-01

We present a simple ultraviolet sub-nanosecond pulse generator using commercial ultraviolet light-emitting diodes with peak emission wavelengths of 290 nm, 318 nm, 338 nm, and 405 nm. The generator is based on step recovery diode, short-circuited transmission line, and current-shaping circuit. The narrowest pulses achieved have 630 ps full width at half maximum at repetition rate of 80 MHz. Optical pulse power in the range of several hundreds of microwatts depends on the applied bias voltage. The bias voltage dependences of the output optical pulse width and peak power are analysed and discussed. Compared to commercial UV sub-nanosecond generators, the proposed generator can produce much higher pulse repetition rate and peak power.

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.

Inscription of type I and depressed cladding waveguides in lithium niobate using a femtosecond laser.

PubMed

Bhardwaj, S; Mittholiya, K; Bhatnagar, A; Bernard, R; Dharmadhikari, J A; Mathur, D; Dharmadhikari, A K

2017-07-10

We describe two types of waveguides (type I and depressed cladding) inscribed in lithium niobate using a variable repetition rate (200 kHz-25 MHz), 270 fs duration fiber laser. The type I modification-based waveguides have propagation losses in the range from 1.2 to 10 dB/cm at 1550 nm, depending on experimental parameters. These waveguides are not permanent; they deteriorate over time. Such deterioration of waveguides can be slowed down from 30 days to 100 days by pre-annealing the samples and by writing at a 720 kHz laser repetition rate. The propagation losses measured at 1550 nm show significant improvement for pre-annealed samples. The depressed cladding-inscribed waveguides are permanent, but the propagation loss depends on the number of damage tracks. A track separation of ∼1  μm between adjacent damage tracks yields the lowest propagation loss of 0.5 dB/cm at 1550 nm for a 40 μm diameter waveguide. We observe multimode guidance for sizes in the range of 20-80 μm in these waveguide structures at 1550 nm. Their crystalline nature is found to remain intact, as inferred from second-harmonic generation within the waveguide region.

The role of stimulus-specific adaptation in songbird syntax generation

NASA Astrophysics Data System (ADS)

Wittenbach, Jason D.

Sequential behaviors are an important part of the behavioral repertoire of many animals and understanding how neural circuits encode and generate such sequences is a long-standing question in neuroscience. The Bengalese finch is a useful model system for studying variable action sequences. The songs of these birds consist of well-defined vocal elements (syllables) that are strung together to form sequences. The ordering of the syllables within the sequence is variable but not random - it shows complex statistical patterns (syntax). While often thought to be first-order, the syntax of the Bengalese finch song shows a distinct form of history dependence where the probability of repeating a syllable decreases as a function of the number of repetitions that have already occurred. Current models of the Bengalese finch song control circuitry offer no explanation for this repetition adaptation. The Bengalese finch also uses real-time auditory feedback to control the song syntax. Considering these facts, we hypothesize that repetition adaptation in the Bengalese finch syntax may be caused by stimulus-specific adaptation - a wide-spread phenomenon where neural responses to a specific stimulus become weaker with repeated presentations of the same stimulus. We begin by proposing a computational model for the song-control circuit where an auditory feedback signal that undergoes stimulus-specific adaptation helps drive repeated syllables. We show that this model does indeed capture the repetition adaptation observed in Bengalese finch syntax; along the way, we derive a new probabilistic model for repetition adaptation. Key predictions of our model are analyzed in light of experiments performed by collaborators. Next we extend the model in order to predict how the syntax will change as a function of brain temperature. These predictions are compared to experimental results from collaborators where portions of the Bengalese finch song circuit are cooled in awake and behaving birds. Finally we show that repetition adaptation persists even in a simplified dynamical system model when a parameter controlling the repeat probability changes slowly over repetitions.

Application of the Repetitive Behavior Scale-Revised--Italian version--in preschoolers with autism spectrum disorder.

PubMed

Fulceri, Francesca; Narzisi, Antonio; Apicella, Fabio; Balboni, Giulia; Baldini, Sara; Brocchini, Jenny; Domenici, Ilaria; Cerullo, Sonia; Igliozzi, Roberta; Cosenza, Angela; Tancredi, Raffaella; Muratori, Filippo; Calderoni, Sara

2016-01-01

Restricted repetitive and stereotyped patterns of behavior, interests, and activities (RRB) are mandatory features for a diagnosis of Autism Spectrum Disorder (ASD) according to the Diagnostic and Statistical Manual of mental disorders-fifth edition (DSM-5). Despite the strong diagnostic role of RRB, their expressiveness and their relationship with other clinical/demographic features in ASD is not fully elucidated. The Italian version of the Repetitive Behavior Scale-Revised (RBS-R) was applied to a relatively large sample of preschool-aged children with ASD who underwent a comprehensive clinical assessment. The relationship between RRB and sex, age, non-verbal IQ, autism severity, as well as the diagnostic accuracy of the RBS-R were explored. Stereotyped and Ritualistic/Sameness behaviors were the most common RRB in preschoolers with ASD, without widespread differences between males and females. No significant correlations between RRB and chronological age, or non-verbal IQ were detected. The expressiveness of ritualistic/sameness behaviors positively correlated with autism severity, assessed through the Calibrated Severity Score (CSS) derived from the Autism Diagnostic Observation Schedule (ADOS). Receiver Operator Characteristic (ROC) analysis showed high diagnostic accuracy using the Global Rating Score, which represents the judgment of the parents of as the RRB affect the child's life. However, while the Global Rating Score performed well, the remaining subscales did not. This investigation extends the limited research on early pattern and associated features of RRB in young children with ASD. The use of the RBS-R may increase the knowledge of the RRB complexity and variability and in turn improve the diagnostic and therapeutic procedures within the autistic spectrum. Copyright © 2015 Elsevier Ltd. All rights reserved.

Self-Rated Accuracy of Rating of Perceived Exertion-Based Load Prescription in Powerlifters.

PubMed

Helms, Eric R; Brown, Scott R; Cross, Matt R; Storey, Adam; Cronin, John; Zourdos, Michael C

2017-10-01

This study assessed male (n = 9) and female (n = 3) powerlifters' (18-49 years) ability to select loads using the repetitions in reserve-based rating of perceived exertion (RPE) scale for a single set for squat, bench press, and deadlift. Subjects trained 3× per week. For 3 weeks on nonconsecutive days in the weekly order of hypertrophy (8 repetitions at 8 RPE), power (2 repetitions at 8 RPE), and strength (3 repetitions at 9 RPE), using subject-selected loads intended to match the target RPE. Bench press and squat were performed every session and deadlift during strength and power only. Mean absolute RPE differences (|reported RPE-target RPE|) ranged from 0.22-0.44, with a mean of 0.33 ± 0.28 RPE. There were no significant RPE differences within lifts between sessions for squat or deadlift. However, bench press was closer to the target RPE for strength (0.15 ± 0.42 RPE) vs. power (-0.21 ± 0.35 RPE, p = 0.05). There were no significant differences within session between lifts for power and strength. However, bench press was closer (0.14 ± 0.44 RPE) to the target RPE than squat (-0.19 ± 0.21 RPE) during hypertrophy (p = 0.02). Squat power was closer to the target RPE in week 3 (0.08 ± 0.29 RPE) vs. 1 (-0.46 ± 0.69 RPE, p = 0.03). It seems that powerlifters can accurately select loads to reach a prescribed RPE. However, accuracy for 8-repetition sets at 8 RPE may be better for bench press compared with squat. Rating squat power-type training may take 3 weeks to reach peak accuracy. Finally, bench press RPE accuracy seems better closer rather than further from failure (i.e., 3-repetition 9 RPE sets vs. 2-repetition 8 RPE sets).

Nonword Repetition with Spectrally Reduced Speech: Some Developmental and Clinical Findings from Pediatric Cochlear Implantation

ERIC Educational Resources Information Center

Burkholder-Juhasz, Rose A.; Levi, Susannah V.; Dillon, Caitlin M.; Pisoni, David B.

2007-01-01

Nonword repetition skills were examined in 24 pediatric cochlear implant (CI) users and 18 normal-hearing (NH) adult listeners listening through a CI simulator. Two separate groups of NH adult listeners assigned accuracy ratings to the nonword responses of the pediatric CI users and the NH adult speakers. Overall, the nonword repetitions of…

Thought Speed, Mood, and the Experience of Mental Motion.

PubMed

Pronin, Emily; Jacobs, Elana

2008-11-01

This article presents a theoretical account relating thought speed to mood and psychological experience. Thought sequences that occur at a fast speed generally induce more positive affect than do those that occur slowly. Thought speed constitutes one aspect of mental motion. Another aspect involves thought variability, or the degree to which thoughts in a sequence either vary widely from or revolve closely around a theme. Thought sequences possessing more motion (occurring fast and varying widely) generally produce more positive affect than do sequences possessing little motion (occurring slowly and repetitively). When speed and variability oppose each other, such that one is low and the other is high, predictable psychological states also emerge. For example, whereas slow, repetitive thinking can prompt dejection, fast, repetitive thinking can prompt anxiety. This distinction is related to the fact that fast thinking involves greater actual and felt energy than slow thinking does. Effects of mental motion occur independent of the specific content of thought. Their consequences for mood and energy hold psychotherapeutic relevance. © 2008 Association for Psychological Science.

Frequency and Predictors of Courses Repetition, Probation, and Delayed Graduation in Kashan Faculty of Nursing and Midwifery

PubMed Central

Tagharrobi, Zahra; Masoudi Alavi, Negin; Fakharian, Esmail; Mirhoseini, Fakhrossadat; Rasoulinejad, Sayyed Asghar; Akbari, Hossein; Ameli, Hossein

2013-01-01

Background: Course failing and delayed graduation are important concerns in educational systems. The reasons of these educational failures need to be clarified. Objectives: This study was designed to determine the academic failure rate and its predictors in Nursing and Midwifery Students in Kashan University of Medical Sciences. Materials and Methods: In this cross-sectional study, the records of all the students graduated in Nursing and Midwifery faculty during 18 years (1986 - 2003) were evaluated (1174 graduates). The demographic variables and the educational situation were recorded. The frequency of course repetition, probation, and delayed graduation were determined and the data were analyzed using the chi-square and logistic regression tests. Results: The frequency of course repetition, probation, and delayed graduation was reported to be 19.25%, 3.9% and 19.85%, respectively. Gaining Low grade in high school, transferring from other universities, having special quota, and transferring temporarily to other universities were mentioned as the risk factors of academic failure. The major had a significant relationship with academic failure. Day time students had more course failure and night time students stayed longer in the university. Conclusions: The individual characteristics, educational background and admission criteria had showed relation with academic failure. Vulnerable students should be identified and educational supports should be provided for these students. PMID:25414885

Differentiating youth who are bullied from other victims of peer-aggression: the importance of differential power and repetition.

PubMed

Ybarra, Michele L; Espelage, Dorothy L; Mitchell, Kimberly J

2014-08-01

To examine whether (1) among youth who report being bullied, differential power and repetition are useful in identifying youth who are more or less affected by the victimization experience and (2) bullying and more generalized peer aggression are distinct or overlapping constructs. Data for the Teen Health and Technology study were collected online between August 2010 and January 2011 from 3,989 13- to 18-year-olds. Data from the Growing up with Media study (Wave 3) were collected online in 2008 from 1,157 12- to 17-year-olds. In the Teen Health and Technology study, youth who reported neither differential power nor repetition had the lowest rates of interference with daily functioning. Youth who reported either differential power or repetition had higher rates, but the highest rates of interference with daily functioning were observed among youth who reported both differential power and repetition. In the Growing up with Media study, youth were victims of online generalized peer aggression (30%) or both online generalized peer aggression and cyberbullying (16%) but rarely cyberbullying alone (1%). Both differential power and repetition are key in identifying youth who are bullied and at particular risk for concurrent psychosocial challenge. Each feature needs to be measured directly. Generalized peer aggression appears to be a broader form of violence compared with bullying. It needs to be recognized that youth who are victimized but do not meet the criteria of bullying have elevated rates of problems. They are an important, albeit nonbullied, group of victimized youth to be included in research. Copyright © 2014 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

Pulsed Electric Propulsion Thrust Stand Calibration Method

NASA Technical Reports Server (NTRS)

Wong, Andrea R.; Polzin, Kurt A.; Pearson, J. Boise

2011-01-01

The evaluation of the performance of any propulsion device requires the accurate measurement of thrust. While chemical rocket thrust is typically measured using a load cell, the low thrust levels associated with electric propulsion (EP) systems necessitate the use of much more sensitive measurement techniques. The design and development of electric propulsion thrust stands that employ a conventional hanging pendulum arm connected to a balance mechanism consisting of a secondary arm and variable linkage have been reported in recent publications by Polzin et al. These works focused on performing steady-state thrust measurements and employed a static analysis of the thrust stand response. In the present work, we present a calibration method and data that will permit pulsed thrust measurements using the Variable Amplitude Hanging Pendulum with Extended Range (VAHPER) thrust stand. Pulsed thrust measurements are challenging in general because the pulsed thrust (impulse bit) occurs over a short timescale (typically 1 micros to 1 millisecond) and cannot be resolved directly. Consequently, the imparted impulse bit must be inferred through observation of the change in thrust stand motion effected by the pulse. Pulsed thrust measurements have typically only consisted of single-shot operation. In the present work, we discuss repetition-rate pulsed thruster operation and describe a method to perform these measurements. The thrust stand response can be modeled as a spring-mass-damper system with a repetitive delta forcing function to represent the impulsive action of the thruster.

A clinical repetitive transcranial magnetic stimulation service in Australia: 6 years on.

PubMed

Galletly, Cherrie A; Clarke, Patrick; Carnell, Benjamin L; Gill, Shane

2015-11-01

There is considerable research evidence for the effectiveness of repetitive transcranial magnetic stimulation in the treatment of depression. However, there is little information about its acceptability and outcomes in clinical settings. This naturalistic study reports on a clinical repetitive transcranial magnetic stimulation service that has been running in Adelaide, South Australia (SA), for 6 years. During this time, 214 complete acute courses were provided to patients with treatment-resistant Major Depressive Disorder. Patients received either sequential bilateral or right unilateral repetitive transcranial magnetic stimulation treatment involving either 18 or 20 sessions given over 6 or 4 weeks respectively. Data included patient demographic details, duration of depression, and medication at the beginning of their repetitive transcranial magnetic stimulation course. The Hamilton Depression Rating Scale was used to assess response to repetitive transcranial magnetic stimulation. Of those undergoing a first-time acute treatment course of repetitive transcranial magnetic stimulation (N = 167), 28% achieved remission, while a further 12% met the criteria for a response to treatment. Most patients (N = 123, 77%) had previously been treated with five or more antidepressant medications, and 77 (47%) had previously received electroconvulsive therapy. Referral rates remained high over the 6 years, indicating acceptance of the treatment by referring psychiatrists. There were no significant adverse events, and the treatment was generally well tolerated. In all, 41 patients (25%) had a second course of repetitive transcranial magnetic stimulation and 6 (4%) patients had a third course; 21 patients subsequently received maintenance repetitive transcranial magnetic stimulation. This naturalistic study showed that repetitive transcranial magnetic stimulation was well accepted by both psychiatrists and patients, and has good efficacy and safety. Furthermore, repetitive transcranial magnetic stimulation can provide a useful treatment alternative as part of outpatient mental health services for people with depression. © The Royal Australian and New Zealand College of Psychiatrists 2015.

Effect of set configuration on hemodynamics and cardiac autonomic modulation after high-intensity squat exercise.

PubMed

Iglesias-Soler, Eliseo; Boullosa, Daniel A; Carballeira, Eduardo; Sánchez-Otero, Tania; Mayo, Xian; Castro-Gacio, Xabier; Dopico, Xurxo

2015-07-01

The aim of this study was to compare the effect of two different high-intensity resistance exercise (RE) set configurations on the following: systolic blood pressure (SBP), rate pressure product (RPP), heart rate (HR) variability (HRV), and HR complexity (HRC). Ten well-trained males performed three parallel squat sets until failure (traditional training; TT) with the four repetitions maximum load (4RM), and a rest of 3 min between sets. Thereafter, participants performed a cluster training session (CT) of equated load but with resting time distributed between each repetition. Dependent variables were recorded before, during, and after RE. Mean SBP (25·7 versus 10·9% percentage increase; P = 0·016) and RPP (112·5 versus 69·9%; P = 0·01) were significantly higher in TT. The decrease in HRV after exercise and the drop of HRC during exercise were similar in CT and TT. Change of standard deviation of normal RR intervals after TT correlated with change in SBP (r = 0·803; P = 0·009) while the change of Sample Entropy during exercise correlated with the increment of RPP during CT (ρ = -0·667; P = 0·05). This study suggests that set configuration influences acute cardiovascular responses during RE. When intensity, volume and work-to-rest ratio are equated, CT is less demanding in terms of SBP and RPP. A greater hemodynamic response during exercise would be associated with a faster parasympathetic recovery. © 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Movement Repetitions in Physical and Occupational Therapy during Spinal Cord Injury Rehabilitation

PubMed Central

Zbogar, Dominik; Eng, Janice J; Miller, William C; Krassioukov, Andrei V; Verrier, Molly C

2016-01-01

Study Design Longitudinal observational study. Objective To quantify the amount of upper and lower extremity movement repetitions (i.e., voluntary movements as part of a functional task or specific motion) occurring during inpatient spinal cord injury (SCI) physical (PT) and occupational therapy (OT), and examine changes over the inpatient rehabilitation stay. Setting Two stand-alone inpatient SCI rehabilitation centres. Methods Participants 103 patients were recruited through consecutive admissions to SCI rehabilitation. Interventions Trained assistants observed therapy sessions and obtained clinical outcome measures in the second week following admission and in the second to last week prior to discharge. Main Outcome Measures PT and OT time, upper and lower extremity repetitions, and changes in these outcomes over the rehabilitation stay. Results We observed 561 PT and 347 OT sessions. Therapeutic time comprised two-thirds of total therapy time. Summed over PT and OT, median upper extremity repetitions in patients with paraplegia were 7 repetitions and in patients with tetraplegia, 42 repetitions. Lower extremity repetitions and steps primarily occurred in ambulatory patients and amounted to 218 and 115, respectively (summed over PT and OT sessions at discharge). Wilcoxon signed rank tests revealed that most repetition variables did not change significantly over the inpatient rehabilitation stay. In contrast, clinical outcomes for the arm and leg improved over this time period. Conclusions Repetitions of upper and lower extremity movement are markedly low during PT and OT sessions. Despite improvements in clinical outcomes, there was no significant increase in movement repetitions over the inpatient rehabilitation stay. PMID:27752057

High-repetition-rate optical delay line using a micromirror array and galvanometer mirror for a terahertz system.

PubMed

Kitahara, Hideaki; Tani, Masahiko; Hangyo, Masanori

2009-07-01

We developed a high-repetition-rate optical delay line based on a micromirror array and galvanometer mirror for terahertz time-domain spectroscopy. The micromirror array is fabricated by using the x-ray lithographic technology. The measurement of terahertz time-domain waveforms with the new optical delay line is demonstrated successfully up to 25 Hz.

The High-Repetition-Rate Advanced Petawatt Laser System

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

Haefner, Constantin; Jarboe, Jeff; Koubikova, Luci

2017-02-02

The High-Repetition-Rate Advanced Petawatt Laser System (HAPLS), being developed at Lawrence Livermore National Laboratory (LLNL), recently completed a significant milestone: demonstration of continuous operation of an all diode-pumped, high-energy femtosecond petawatt laser system. The system is now ready for delivery and integration at the European Extreme Light Infrastructure Beamlines facility project (ELI Beamlines) in the Czech Republic.

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.

Optically stabilized Erbium fiber frequency comb with hybrid mode-locking and a broad tunable range of repetition rate.

PubMed

Yang, Honglei; Wu, Xuejian; Zhang, Hongyuan; Zhao, Shijie; Yang, Lijun; Wei, Haoyun; Li, Yan

2016-12-01

We present an optically stabilized Erbium fiber frequency comb with a broad repetition rate tuning range based on a hybrid mode-locked oscillator. We lock two comb modes to narrow-linewidth reference lasers in turn to investigate the best performance of control loops. The control bandwidth of fast and slow piezoelectric transducers reaches 70 kHz, while that of pump current modulation with phase-lead compensation is extended to 32 kHz, exceeding laser intrinsic response. Eventually, simultaneous lock of both loops is realized to totally phase-stabilize the comb, which will facilitate precision dual-comb spectroscopy, laser ranging, and timing distribution. In addition, a 1.8-MHz span of the repetition rate is achieved by an automatic optical delay line that is helpful in manufacturing a secondary comb with a similar repetition rate. The oscillator is housed in a homemade temperature-controlled box with an accuracy of ±0.02  K, which not only keeps high signal-to-noise ratio of the beat notes with reference lasers, but also guarantees self-starting at the same mode-locking every time.

Separation Control in a Multistage Compressor Using Impulsive Surface Injection

NASA Technical Reports Server (NTRS)

Wundrow, David W.; Braunscheidel, Edward P.; Culley, Dennis E.; Bright, Michelle M.

2006-01-01

Control of flow separation using impulsive surface injection is investigated within the multistage environment of a low speed axial-flow compressor. Measured wake profiles behind a set of embedded stator vanes treated with suction-surface injection indicate significant reduction in flow separation at a variety of injection-pulse repetition rates and durations. The corresponding total pressure losses across the vanes reveal a bank of repetition rates at each pulse duration where the separation control remains nearly complete. This persistence allows for demands on the injected-mass delivery system to be economized while still achieving effective flow control. The response of the stator-vane boundary layers to infrequently applied short injection pulses is described in terms of the periodic excitation of turbulent strips whose growth and propagation characteristics dictate the lower bound on the band of optimal pulse repetition rates. The eventual falloff in separation control at higher repetition rates is linked to a competition between the benefits of pulse-induced mixing and the aggravation caused by the periodic introduction of low-momentum fluid. Use of these observations for impulsive actuator design is discussed and their impact on modeling the time-average effect of impulsive surface injection for multistage steady-flow simulation is considered.

Channel-parameter estimation for satellite-to-submarine continuous-variable quantum key distribution

NASA Astrophysics Data System (ADS)

Guo, Ying; Xie, Cailang; Huang, Peng; Li, Jiawei; Zhang, Ling; Huang, Duan; Zeng, Guihua

2018-05-01

This paper deals with a channel-parameter estimation for continuous-variable quantum key distribution (CV-QKD) over a satellite-to-submarine link. In particular, we focus on the channel transmittances and the excess noise which are affected by atmospheric turbulence, surface roughness, zenith angle of the satellite, wind speed, submarine depth, etc. The estimation method is based on proposed algorithms and is applied to low-Earth orbits using the Monte Carlo approach. For light at 550 nm with a repetition frequency of 1 MHz, the effects of the estimated parameters on the performance of the CV-QKD system are assessed by a simulation by comparing the secret key bit rate in the daytime and at night. Our results show the feasibility of satellite-to-submarine CV-QKD, providing an unconditionally secure approach to achieve global networks for underwater communications.

Accurate modeling of high-repetition rate ultrashort pulse amplification in optical fibers

PubMed Central

Lindberg, Robert; Zeil, Peter; Malmström, Mikael; Laurell, Fredrik; Pasiskevicius, Valdas

2016-01-01

A numerical model for amplification of ultrashort pulses with high repetition rates in fiber amplifiers is presented. The pulse propagation is modeled by jointly solving the steady-state rate equations and the generalized nonlinear Schrödinger equation, which allows accurate treatment of nonlinear and dispersive effects whilst considering arbitrary spatial and spectral gain dependencies. Comparison of data acquired by using the developed model and experimental results prove to be in good agreement. PMID:27713496

A Perceptual Repetition Blindness Effect

NASA Technical Reports Server (NTRS)

Hochhaus, Larry; Johnston, James C.; Null, Cynthia H. (Technical Monitor)

1994-01-01

Before concluding Repetition Blindness is a perceptual phenomenon, alternative explanations based on memory retrieval problems and report bias must be rejected. Memory problems were minimized by requiring a judgment about only a single briefly displayed field. Bias and sensitivity effects were empirically measured with an ROC-curve analysis method based on confidence ratings. Results from five experiments support the hypothesis that Repetition Blindness can be a perceptual phenomenon.

A cavity-dumped and regenerative amplifier system for generating high-energy, high-repetition-rate picosecond pulses

NASA Astrophysics Data System (ADS)

Peng, ZhiGang; Chen, Meng; Yang, Chao; Chang, Liang; Li, Gang

2015-02-01

We report a high-energy, high-repetition CW pumped Nd:YVO4 amplifier system, that produces 10.5 W, 14.2 ps pulses at 1064 nm wavelength and 5 W pulses at 532 nm wavelength with a repetition rate of 10 kHz. Pulses from a passively mode-locked Nd:YVO4 oscillator are first generated by cavity dumping, and then further amplified in a regenerative amplifier from 545 nJ to 1 mJ with a CW diode-pumped Nd:YVO4. After frequency doubling, 0.5 mJ pulses are obtained with a wavelength of 532 nm.

Characterization of a high repetition-rate laser-driven short-pulsed neutron source

NASA Astrophysics Data System (ADS)

Hah, J.; Nees, J. A.; Hammig, M. D.; Krushelnick, K.; Thomas, A. G. R.

2018-05-01

We demonstrate a repetitive, high flux, short-pulsed laser-driven neutron source using a heavy-water jet target. We measure neutron generation at 1/2 kHz repetition rate using several-mJ pulse energies, yielding a time-averaged neutron flux of 2 × 105 neutrons s‑1 (into 4π steradians). Deuteron spectra are also measured in order to understand source characteristics. Analyses of time-of-flight neutron spectra indicate that two separate populations of neutrons, ‘prompt’ and ‘delayed’, are generated at different locations. Gamma-ray emission from neutron capture 1H(n,γ) is also measured to confirm the neutron flux.

Group velocity locked vector dissipative solitons in a high repetition rate fiber laser

NASA Astrophysics Data System (ADS)

Luo, Yiyang; Li, Lei; Liu, Deming; Sun, Qizhen; Wu, Zhichao; Xu, Zhilin; Tang, Dingyuan; Fu, Songnian; Zhao, Luming

2016-08-01

Vectorial nature of dissipative solitons (DSs) with high repetition rates is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectra, which can be considered as an auxiliary indicator of the group velocity locked vector DSs.

Low-threshold, nanosecond, high-repetition-rate vortex pulses with controllable helicity generated in Cr,Nd:YAG self-Q-switched microchip laser

NASA Astrophysics Data System (ADS)

He, Hong-Sen; Chen, Zhen; Li, Hong-Bin; Dong, Jun

2018-05-01

A high repetition rate, nanosecond, pulsed optical vortex beam has been generated in a Cr,Nd:YAG self-Q-switched microchip laser pumped by the annular-beam formed with a hollow focus lens. The lasing threshold for vortex pulses is 0.9 W. A pulse width of 6.5 ns and a repetition rate of over 330 kHz have been achieved. The average output power of 1 W and the slope efficiency of 46.6% have been obtained. The helicity of the optical vortices has been controlled by adjusting the tilted angle between Cr,Nd:YAG crystal and output coupler. The work provides a new method for developing pulsed optical vortices for potential applications on quantum communication and optical trapping.

Controlling laser driven protons acceleration using a deformable mirror at a high repetition rate

NASA Astrophysics Data System (ADS)

Noaman-ul-Haq, M.; Sokollik, T.; Ahmed, H.; Braenzel, J.; Ehrentraut, L.; Mirzaie, M.; Yu, L.-L.; Sheng, Z. M.; Chen, L. M.; Schnürer, M.; Zhang, J.

2018-03-01

We present results from a proof-of-principle experiment to optimize laser driven protons acceleration by directly feeding back its spectral information to a deformable mirror (DM) controlled by evolutionary algorithms (EAs). By irradiating a stable high-repetition rate tape driven target with ultra-intense pulses of intensities ∼1020 W/ cm2, we optimize the maximum energy of the accelerated protons with a stability of less than ∼5% fluctuations near optimum value. Moreover, due to spatio-temporal development of the sheath field, modulations in the spectrum are also observed. Particularly, a prominent narrow peak is observed with a spread of ∼15% (FWHM) at low energy part of the spectrum. These results are helpful to develop high repetition rate optimization techniques required for laser-driven ion accelerators.

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

Cryogenic cooling for high power laser amplifiers

NASA Astrophysics Data System (ADS)

Perin, J. P.; Millet, F.; Divoky, M.; Rus, B.

2013-11-01

Using DPSSL (Diode Pumped Solid State Lasers) as pumping technology, PW-class lasers with enhanced repetition rates are developed. Each of the Yb YAG amplifiers will be diode-pumped at a wavelength of 940 nm. This is a prerequisite for achieving high repetition rates (light amplification duration 1 millisecond and repetition rate 10 Hz). The efficiency of DPSSL is inversely proportional to the temperature, for this reason the slab amplifier have to be cooled at a temperature in the range of 100 K-170 K with a heat flux of 1 MW*m-2. This paper describes the thermo-mechanical analysis for the design of the amplification laser head, presents a preliminary proposal for the required cryogenic cooling system and finally outlines the gain of cryogenic operation for the efficiency of high pulsed laser.

Forms of work organization and associations with shoulder disorders: Results from a French working population.

PubMed

Bodin, Julie; Garlantézec, Ronan; Costet, Nathalie; Descatha, Alexis; Fouquet, Natacha; Caroly, Sandrine; Roquelaure, Yves

2017-03-01

The aim of this study was to identify forms of work organization in a French region and to study associations with the occurrence of symptomatic and clinically diagnosed shoulder disorders in workers. Workers were randomly included in this cross-sectional study from 2002 to 2005. Sixteen organizational variables were assessed by a self-administered questionnaire: i.e. shift work, job rotation, repetitiveness of tasks, paced work/automatic rate, work pace dependent on quantified targets, permanent controls or surveillance, colleagues' work and customer demand, and eight variables measuring decision latitude. Five forms of work organization were identified using hierarchical cluster analysis (HCA) of variables and HCA of workers: low decision latitude with pace constraints, medium decision latitude with pace constraints, low decision latitude with low pace constraints, high decision latitude with pace constraints and high decision latitude with low pace constraints. There were significant associations between forms of work organization and symptomatic and clinically-diagnosed shoulder disorders. Copyright © 2016 Elsevier Ltd. All rights reserved.

Relation of Psychiatric Symptoms with Epilepsy, Asthma, and Allergy in Youth with ASD vs. Psychiatry Referrals.

PubMed

Weber, Rebecca J; Gadow, Kenneth D

2017-08-01

The present study aimed to characterize the association of psychopathology with the clinical correlates of epilepsy, asthma, and allergy within and between neurobehavioral syndromes. Participants were consecutively evaluated youth (6-18 years, 75 % male) with autism spectrum disorder (ASD; n = 589) and non-ASD outpatient psychiatry referrals (n = 653). Informants completed a background questionnaire (parents) and a psychiatric symptom severity rating scale (parents, teachers). Youth with ASD had higher rates of epilepsy and allergy but not asthma than psychiatry referrals, even when analyses were limited to youth with IQ ≥ 70. Somatic conditions evidenced variable associations with medical services utilization, educational interventions, family income, and maternal education. Youth with ASD with versus without epilepsy had more severe ASD social deficits (parents' ratings) and less severe ASD repetitive behaviors (teachers' ratings). Epilepsy was associated with more severe depression, mania, and schizophrenia symptoms in youth with ASD. Youth with allergy (psychiatry referrals only) had more severe anxiety and depression symptoms (parents' ratings) but less severe aggression (teachers' ratings) thus providing evidence of both context- and diagnostic-specificity. Youth with ASD versus non-ASD psychiatry referrals evidence a variable pattern of relations between somatic conditions and a range of clinical correlates, which suggests that the biologic substrates and psychosocial concomitants of neurodevelopmental disorders and their co-occurring somatic conditions may interact to produce unique clinical phenotypes.

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

Variation, Repetition, and Choice

ERIC Educational Resources Information Center

Abreu-Rodrigues, Josele; Lattal, Kennon A.; dos Santos, Cristiano V.; Matos, Ricardo A.

2005-01-01

Experiment 1 investigated the controlling properties of variability contingencies on choice between repeated and variable responding. Pigeons were exposed to concurrent-chains schedules with two alternatives. In the REPEAT alternative, reinforcers in the terminal link depended on a single sequence of four responses. In the VARY alternative, a…

Laser-diode pumped self-mode-locked praseodymium visible lasers with multi-gigahertz repetition rate.

PubMed

Zhang, Yuxia; Yu, Haohai; Zhang, Huaijin; Di Lieto, Alberto; Tonelli, Mauro; Wang, Jiyang

2016-06-15

We demonstrate efficient laser-diode pumped multi-gigahertz (GHz) self-mode-locked praseodymium (Pr³⁺) visible lasers with broadband spectra from green to deep red for the first time to our knowledge. With a Pr³⁺-doped GdLiF₄ crystal, stable self-mode-locked visible pulsed lasers at the wavelengths of 522 nm, 607 nm, 639 nm, and 720 nm have been obtained with the repetition rates of 2.8 GHz, 3.1 GHz, 3.1 GHz, and 3.0 GHz, respectively. The maximum output power was 612 mW with the slope efficiency of 46.9% at 639 nm. The mode-locking mechanism was theoretically analyzed. The stable second-harmonic mode-locking with doubled repetition frequency was also realized based on the Fabry-Perot effect formed in the laser cavity. In addition, we find that the polarization directions were turned with lasing wavelengths. This work may provide a new way for generating efficient ultrafast pulses with high- and changeable-repetition rates in the visible range.

Acoustic-wave-damping experimental study in x-ray preionized high-repetition rate XeCl

NASA Astrophysics Data System (ADS)

Canarelli, Patrick; Sentis, Marc L.; Delaporte, Philippe C.; Fontaine, Bernard L.; Forestier, Bernard M.

1990-08-01

To increase the pulse repetition frequency, the average power, and the beam quality of excimer laser systems, damping of the strong acoustic waves induced by the active medium excitation must be solve. In order to achieve this goal different electrodes and acoustic damping configuration have been studied. Excitation of active medium (energy deposition : 50 to 150 J/l) at high repetition rate (up to 1 000 Hz) in a subsonic loop (flow velocity : up to 65 m/s) is achieved by means of a classical discharge, through transfers capacitors. The discharge is preionized by X-Ray generated by a wire ion plasma gun. Previous studies done at I.M.F.M. have shown that the density perturbations, induced by successive excitations at high repetition rate (up to 1000 Hz), can involve output energy decrease. Here, we will present and discuss the density or pressure perturbation maximum level which don't involve this laser energy decrease; acoustic and thermal effects have been notably took account. We will study the possibilities of fast pressure perturbations damping.

High repetition rate, high energy, actively Q-switched all-in-fiber laser

NASA Astrophysics Data System (ADS)

Lecourt, J. B.; Bertrand, A.; Guillemet, S.; Hernandez, Y.; Giannone, D.

2010-05-01

We report an actively Q-switched Ytterbium-doped all-in-fibre laser delivering 10ns pulses with high repetition rate (from 100kHz to 1MHz). The laser operation has been validated at three different wavelengths (1040, 1050 and 1064nm). The laser can deliver up to 20Watts average power with an high beam quality (M2 = 1).

Passively mode-locked Raman fiber laser with 100 GHz repetition rate

NASA Astrophysics Data System (ADS)

Schröder, Jochen; Coen, Stéphane; Vanholsbeeck, Frédérique; Sylvestre, Thibaut

2006-12-01

We experimentally demonstrate the operation of a passively mode-locked Raman fiber ring laser with an ultrahigh repetition rate of 100GHz and up to 430mW of average output power. This laser constitutes a simple wavelength versatile pulsed optical source. Stable mode locking is based on dissipative four-wave mixing with a single fiber Bragg grating acting as the mode-locking element.

Repetitive negative thinking predicts depression and anxiety symptom improvement during brief cognitive behavioral therapy.

PubMed

Kertz, Sarah J; Koran, Jennifer; Stevens, Kimberly T; Björgvinsson, Thröstur

2015-05-01

Repetitive negative thinking (RNT) is a common symptom across depression and anxiety disorders and preliminary evidence suggests that decreases in rumination and worry are related to improvement in depression and anxiety symptoms. However, despite its prevalence, relatively little is known about transdiagnostic RNT and its temporal associations with symptom improvement during treatment. The current study was designed to examine the influence of RNT on subsequent depression and anxiety symptoms during treatment. Participants (n = 131; 52% female; 93% White; M = 34.76 years) were patients presenting for treatment in a brief, cognitive behavior therapy based, partial hospitalization program. Participants completed multiple assessments of depression (Center for the Epidemiological Studies of Depression-10 scale), anxiety (the 7-item Generalized Anxiety Disorder Scale), and repetitive negative thinking (Perseverative Thinking Questionnaire) over the course of treatment. Results indicated statistically significant between and within person effects of RNT on depression and anxiety, even after controlling for the effect of time, previous symptom levels, referral source, and treatment length. RNT explained 22% of the unexplained variability in depression scores and 15% of the unexplained variability in anxiety scores beyond that explained by the control variables. RNT may be an important transdiagnostic treatment target for anxiety and depression. Copyright © 2015 Elsevier Ltd. All rights reserved.

Chromosomal Mapping of Repetitive DNA Sequences in the Genus Bryconamericus (Characidae) and DNA Barcoding to Differentiate Populations.

PubMed

Santos, Angélica Rossotti Dos; Usso, Mariana Campaner; Gouveia, Juceli Gonzalez; Araya-Jaime, Cristian; Frantine-Silva, Wilson; Giuliano-Caetano, Lucia; Foresti, Fausto; Dias, Ana Lúcia

2017-06-01

The mapping of repetitive DNA sites by fluorescence in situ hybridization has been widely used for karyotype studies in different species of fish, especially when dealing with related species or even genera presenting high chromosome variability. This study analyzed three populations of Bryconamericus, with diploid number preserved, but with different karyotype formulae. Bryconamericus ecai, from the Forquetinha river/RS, presented three new cytotypes, increasing the number of karyotype forms to seven in this population. Other two populations of Bryconamericus sp. from the Vermelho stream/PR and Cambuta river/PR exhibited interpopulation variation. The chromosome mapping of rDNA sites revealed unique markings among the three populations, showing inter- and intrapopulation variability located in the terminal region. The molecular analysis using DNA barcoding complementing the cytogenetic analysis also showed differentiation among the three populations. The U2 small nuclear DNA repetitive sequence exhibited conserved features, being located in the interstitial region of a single chromosome pair. This is the first report on its occurrence in the genus Bryconamericus. Data obtained revealed a karyotype variability already assigned to the genus, along with polymorphism of ribosomal sites, demonstrating that this group of fish can be undergoing a divergent evolutionary process, constituting a substantive model for studies of chromosomal evolution.

Shuttle ku-band communications/radar technical concepts

NASA Technical Reports Server (NTRS)

Griffin, J. W.; Kelley, J. S.; Steiner, A. W.; Vang, H. A.; Zrubek, W. E.; Huth, G. K.

1985-01-01

Technical data on the Shuttle Orbiter K sub u-band communications/radar system are presented. The more challenging aspects of the system design and development are emphasized. The technical problems encountered and the advancements made in solving them are discussed. The radar functions are presented first. Requirements and design/implementation approaches are discussed. Advanced features are explained, including Doppler measurement, frequency diversity, multiple pulse repetition frequencies and pulse widths, and multiple modes. The communications functions that are presented include advances made because of the requirements for multiple communications modes. Spread spectrum, quadrature phase shift keying (QPSK), variable bit rates, and other advanced techniques are discussed. Performance results and conclusions reached are outlined.

Femtosecond Laser Eyewear Protection: Measurements and Precautions

PubMed Central

Stromberg, Christopher J.; Hadler, Joshua A.; Alberding, Brian G.; Heilweil, Edwin J.

2018-01-01

Ultrafast laser systems are becoming more widespread throughout the research and industrial communities yet eye protection for these high power, bright pulsed sources still require scrupulous characterization and testing before use. Femtosecond lasers, with pulses naturally possessing broad-bandwidth and high average power with variable repetition rate, can exhibit spectral side-bands and subtly changing center wavelengths, which may unknowingly affect eyewear safety protection. Pulse spectral characterization and power diagnostics are presented for a 80 MHz, Ti+3:Sapphire, ≈ 800 nm, ≈40 femtosecond oscillator system. Power and spectral transmission for 22 test samples are measured to determine whether they fall within manufacturer specifications. PMID:29353984

Femtosecond Laser Eyewear Protection: Measurements and Precautions.

PubMed

Stromberg, Christopher J; Hadler, Joshua A; Alberding, Brian G; Heilweil, Edwin J

2017-11-01

Ultrafast laser systems are becoming more widespread throughout the research and industrial communities yet eye protection for these high power, bright pulsed sources still require scrupulous characterization and testing before use. Femtosecond lasers, with pulses naturally possessing broad-bandwidth and high average power with variable repetition rate, can exhibit spectral side-bands and subtly changing center wavelengths, which may unknowingly affect eyewear safety protection. Pulse spectral characterization and power diagnostics are presented for a 80 MHz, Ti +3 :Sapphire, ≈ 800 nm, ≈40 femtosecond oscillator system. Power and spectral transmission for 22 test samples are measured to determine whether they fall within manufacturer specifications.

Differential Training Facilitates Early Consolidation in Motor Learning

PubMed Central

Henz, Diana; Schöllhorn, Wolfgang I.

2016-01-01

Current research demonstrates increased learning rates in differential learning (DL) compared to repetitive training. To date, little is known on the underlying neurophysiological processes in DL that contribute to superior performance over repetitive practice. In the present study, we measured electroencephalographic (EEG) brain activation patterns after DL and repetitive badminton serve training. Twenty-four semi-professional badminton players performed badminton serves in a DL and repetitive training schedule in a within-subjects design. EEG activity was recorded from 19 electrodes according to the 10–20 system before and immediately after each 20-min exercise. Increased theta activity was obtained in contralateral parieto-occipital regions after DL. Further, increased posterior alpha activity was obtained in DL compared to repetitive training. Results indicate different underlying neuronal processes in DL and repetitive training with a higher involvement of parieto-occipital areas in DL. We argue that DL facilitates early consolidation in motor learning indicated by post-training increases in theta and alpha activity. Further, brain activation patterns indicate somatosensory working memory processes where attentional resources are allocated in processing of somatosensory information in DL. Reinforcing a somatosensory memory trace might explain increased motor learning rates in DL. Finally, this memory trace is more stable against interference from internal and external disturbances that afford executively controlled processing such as attentional processes. PMID:27818627

Temperature rises during application of Er:YAG laser under different primary dentin thicknesses.

PubMed

Hubbezoglu, Ihsan; Unal, Murat; Zan, Recai; Hurmuzlu, Feridun

2013-05-01

The present study investigated the effects of the Er:YAG laser's different pulse repetition rates on temperature rise under various primary dentin thicknesses. The Er:YAG laser can be used for restorative approaches in clinics and is used to treat dental caries. There are some reports that explain the temperature rise effect of the Er:YAG laser. Recently, the Er:YAG laser has been found to play an important role in temperature rises during the application on dentin. Caries-free primary mandibular molars were prepared to obtain dentin discs with 0.5, 1, 1.5, and 2 mm thicknesses (n=10). These discs were placed between the Teflon mold cylinders of a temperature test apparatus. We preferred three pulse repetition rates of 10, 15, and 20 Hz with an energy density of 12.7 J/cm2 and a 230 μs pulse duration. All dentin discs were irradiated for 30 sec by the Er:YAG laser. Temperature rises were recorded using an L-type thermocouple and universal data loggers/scanners (E-680, Elimko Co., Turkey). Data were analyzed by two-way ANOVA and Tukey tests. Whereas the lowest temperature rise (0.44±0.09 °C) was measured from a 10 Hz pulse repetition rate at a dentin thickness of 2 mm, the highest temperature rise (3.86±0.43 °C) was measured from a 20 Hz pulse repetition rate at a 0.5 mm dentin thickness. Temperature rise did not reach critical value for pulpal injury in any primary dentin thicknesses irradiated by a high repetition rate of the Er:YAG laser.

Advanced photoinjector experiment photogun commissioning results

NASA Astrophysics Data System (ADS)

Sannibale, F.; Filippetto, D.; Papadopoulos, C. F.; Staples, J.; Wells, R.; Bailey, B.; Baptiste, K.; Corlett, J.; Cork, C.; De Santis, S.; Dimaggio, S.; Doolittle, L.; Doyle, J.; Feng, J.; Garcia Quintas, D.; Huang, G.; Huang, H.; Kramasz, T.; Kwiatkowski, S.; Lellinger, R.; Moroz, V.; Norum, W. E.; Padmore, H.; Pappas, C.; Portmann, G.; Vecchione, T.; Vinco, M.; Zolotorev, M.; Zucca, F.

2012-10-01

The Advanced Photoinjector Experiment (APEX) at the Lawrence Berkeley National Laboratory is dedicated to the development of a high-brightness high-repetition rate (MHz-class) electron injector for x-ray free-electron laser (FEL) and other applications where high repetition rates and high brightness are simultaneously required. The injector is based on a new concept rf gun utilizing a normal-conducting (NC) cavity resonating in the VHF band at 186 MHz, and operating in continuous wave (cw) mode in conjunction with high quantum efficiency photocathodes capable of delivering the required charge at MHz repetition rates with available laser technology. The APEX activities are staged in three phases. In phase 0, the NC cw gun is built and tested to demonstrate the major milestones to validate the gun design and performance. Also, starting in phase 0 and continuing in phase I, different photocathodes are tested at the gun energy and at full repetition rate for validating candidate materials to operate in a high-repetition rate FEL. In phase II, a room-temperature pulsed linac is added for accelerating the beam at several tens of MeV to reduce space charge effects and allow the measurement of the brightness of the beam from the gun when integrated in an injector scheme. The installation of the phase 0 beam line and the commissioning of the VHF gun are completed, phase I components are under fabrication, and initial design and specification of components and layout for phase II are under way. This paper presents the phase 0 commissioning results with emphasis on the experimental milestones that have successfully demonstrated the APEX gun capability of operating at the required performance.

Simple ps microchip Nd:YVO4 laser with 3.3-ps pulses at 0.2 to 1.4 MHz and single-stage amplification to the microjoule level

NASA Astrophysics Data System (ADS)

Türkyilmaz, Erdal; Lohbreier, Jan; Günther, Christian; Mehner, Eva; Kopf, Daniel; Giessen, Harald; Braun, Bernd

2016-06-01

Commercial picosecond sources have found widespread applications. Typical system parameters are pulse widths below 20 ps, repetition rates between 0.1 and 2 MHz, and microjoule level pulse energies. Most systems are based on short pulse mode-locked oscillators, regenerative amplifiers, and pockel cells as active beam switches. In contrast, we present a completely passive system, consisting of a passively Q-switched microchip laser, a single-stage amplifier, and a pulse compressor. The Q-switched microchip laser has a 50-μm-long Nd:YVO4 gain material optically bonded to a 4.6-mm-thick undoped YVO4 crystal. It delivers pulse widths of 40 ps and repetition rates of 0.2 to 1.4 MHz at a wavelength of 1.064 μm. The pulse energy is a few nanojoule. These 40-ps pulses are spectrally broadened in a standard single-mode fiber and then compressed in a 24-mm-long chirped Bragg grating to as low as 3.3 ps. The repetition rate can be tuned from ˜0.2 to 1.4 MHz by changing the pump power, while the pulse width and the pulse energy from the microchip laser are unchanged. The spectral broadening in the fiber is observed throughout the pulse repetition rate, supporting sub-10-ps pulses. Finally, the pulses are amplified in a single-stage Nd:YVO4 amplifier up to the microjoule level (up to 4 μJ pulse energy). As a result, the system delivers sub-10-ps pulses at a microjoule level with about 1 MHz repetition rate, and thus fulfills the requirements for ps-micromachining. It does not contain any active switching elements and can be integrated in a very compact setup.

Simple ps microchip Nd:YVO4 laser with 3.3 ps pulses at 0.2 - 1.4 MHz and single-stage amplification to the microjoule level

NASA Astrophysics Data System (ADS)

Türkyilmaz, Erdal; Lohbreier, Jan; Günther, Christian; Mehner, Eva; Kopf, Daniel; Giessen, Harald; Braun, Bernd

2016-03-01

Commercial picosecond sources have found widespread applications. Typical system parameters are pulse widths below 20 ps, repetition rates between 0.1 to 2 MHz, and micro Joule level pulse energies. Most systems are based on short pulse modelocked oscillators, regenerative amplifiers, and pockel cells as active beam switches. In contrast we present a completely passive system, consisting of a passively Q-switched microchip laser, a single-stage amplifier, and a pulse compressor. The Q-switched microchip laser has a 50 μm long Nd:YVO4-gain material optically bonded to a 4.6 mm thick undoped YVO4-crystal. It delivers pulse widths of 40 ps and repetition rates of 0.2 - 1.4 MHz at a wavelength of 1.064 μm. The pulse energy is a few nJ. These 40-ps pulses are spectrally broadened in a standard single mode fibre and then compressed in a 24 mm long chirped Bragg grating to as low as 3.3 ps. The repetition rate can be tuned from app. 0.2 to 1.4 MHz by changing the pump power while the pulse width and the pulse energy from the microchip laser are unchanged. The spectral broadening in the fibre is observed throughout the pulse repetition rate, supporting sub-10- ps pulses. Finally, the pulses are amplified in a single-stage Nd:YVO4-amplifier up to the microjoule level (up to 4 μJ pulse energy). As a result the system delivers sub-10-ps pulses at a microjoule level with about 1 MHz repetition rate, and thus fulfills the requirements for ps-micromachining. It does not contain any active switching elements and can be integrated in a very compact setup.

Analysis of magnesium and copper in aluminum alloys with high repetition rate laser-ablation spark-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

He, Xiaoyong; Dong, Bo; Chen, Yuqi; Li, Runhua; Wang, Fujuan; Li, Jiaoyang; Cai, Zhigang

2018-03-01

In order to improve the analytical speed and performance of laser-ablation based atomic emission spectroscopy, high repetition rate laser-ablation spark-induced breakdown spectroscopy (HRR LA-SIBS) was first developed. Magnesium and copper in aluminum alloys were analyzed with this technique. In the experiments, the fundamental output of an acousto-optically Q-switched Nd:YAG laser operated at 1 kHz repetition rate with low pulse energy and 120 ns pulse width was used to ablate the samples and the plasma emission was enhanced by spark discharge. The spectra were recorded with a compact fiber spectrometer with non-intensified charge-coupled device in non-gating mode. Different parameters relative with analytical performance, such as capacitance, voltage, laser pulse energy were optimized. Under current experimental conditions, calibration curves of magnesium and copper in aluminum alloys were built and limits of detection of them were determined to be 14.0 and 9.9 ppm by HRR LA-SIBS, respectively, which were 8-12 folds better than that achieved by HRR LA under similar experimental condition without spark discharge. The analytical sensitivities are close to those obtained with conventional LIBS but with improved analytical speed as well as possibility of using compact fiber spectrometer. Under high repetition rate operation, the noise level can be decreased and the analytical reproducibility can be improved obviously by averaging multiple measurements within short time. High repetition rate operation of laser-ablation spark-induced breakdown spectroscopy is very helpful for improving analytical speed. It is possible to find applications in fast elements analysis, especially fast two-dimension elemental mapping of solid samples.

Verification of Concurrent Programs. Part II. Temporal Proof Principles.

DTIC Science & Technology

1981-09-01

not modify any of the shared program variables. In order to ensure the correct synchronization between the processes we use three semaphore variables...direct, simple, and intuitive rides for the establishment of these properties. rhey usually replace long but repetitively similar chains of primitive ...modify the variables on which Q actually depends. A typical case is that of semaphores . We have the following property: The Semaphore Variable Rule

Menstrual-cycle characteristics and work conditions of workers in poultry slaughterhouses and canneries.

PubMed

Messing, K; Saurel-Cubizolles, M J; Bourgine, M; Kaminski, M

1992-10-01

The food and agriculture industry employs 14.6% of the female industrial work force in France. Workers are exposed to a variety of environmental and organizational constraints (eg, irregular schedules, cold, uncomfortable postures, repetitive movements). In 1987-1988 a medical examination and questionnaire were administered to 726 workers with menstrual periods in 17 poultry slaughterhouses and six canning factories. Anomalies (irregular cycles, amenorrhea, long cycles) during the previous year were associated with work conditions. After adjustment for relevant nonoccupational variables, irregular cycles were significantly related to schedule variability and cold exposure, amenorrhea was associated with cold exposure, and long cycles with schedule variability. Other parameters such as repetitive work, standing posture, lifting weights, job satisfaction, and hours of domestic work were not associated with cycle anomalies. Cycle anomalies may be a useful indicator of occupational effects on female reproduction, analogous to the use of sperm parameters to warn of effects on male workers.

High-repetition-rate interferometric Rayleigh scattering for flow-velocity measurements

NASA Astrophysics Data System (ADS)

Estevadeordal, Jordi; Jiang, Naibo; Cutler, Andrew D.; Felver, Josef J.; Slipchenko, Mikhail N.; Danehy, Paul M.; Gord, James R.; Roy, Sukesh

2018-03-01

High-repetition-rate interferometric-Rayleigh-scattering (IRS) velocimetry is demonstrated for non-intrusive, high-speed flow-velocity measurements. High temporal resolution is obtained with a quasi-continuous burst-mode laser that is capable of operating at 10-100 kHz, providing 10-ms bursts with pulse widths of 5-1000 ns and pulse energy > 100 mJ at 532 nm. Coupled with a high-speed camera system, the IRS method is based on imaging the flow field through an etalon with 8-GHz free spectral range and capturing the Doppler shift of the Rayleigh-scattered light from the flow at multiple points having constructive interference. The seed-laser linewidth permits a laser linewidth of < 150 MHz at 532 nm. The technique is demonstrated in a high-speed jet, and high-repetition-rate image sequences are shown.

Input Variability Facilitates Unguided Subcategory Learning in Adults

PubMed Central

Eidsvåg, Sunniva Sørhus; Austad, Margit; Asbjørnsen, Arve E.

2015-01-01

Purpose This experiment investigated whether input variability would affect initial learning of noun gender subcategories in an unfamiliar, natural language (Russian), as it is known to assist learning of other grammatical forms. Method Forty adults (20 men, 20 women) were familiarized with examples of masculine and feminine Russian words. Half of the participants were familiarized with 32 different root words in a high-variability condition. The other half were familiarized with 16 different root words, each repeated twice for a total of 32 presentations in a high-repetition condition. Participants were tested on untrained members of the category to assess generalization. Familiarization and testing was completed 2 additional times. Results Only participants in the high-variability group showed evidence of learning after an initial period of familiarization. Participants in the high-repetition group were able to learn after additional input. Both groups benefited when words included 2 cues to gender compared to a single cue. Conclusions The results demonstrate that the degree of input variability can influence learners' ability to generalize a grammatical subcategory (noun gender) from a natural language. In addition, the presence of multiple cues to linguistic subcategory facilitated learning independent of variability condition. PMID:25680081

Input Variability Facilitates Unguided Subcategory Learning in Adults.

PubMed

Eidsvåg, Sunniva Sørhus; Austad, Margit; Plante, Elena; Asbjørnsen, Arve E

2015-06-01

This experiment investigated whether input variability would affect initial learning of noun gender subcategories in an unfamiliar, natural language (Russian), as it is known to assist learning of other grammatical forms. Forty adults (20 men, 20 women) were familiarized with examples of masculine and feminine Russian words. Half of the participants were familiarized with 32 different root words in a high-variability condition. The other half were familiarized with 16 different root words, each repeated twice for a total of 32 presentations in a high-repetition condition. Participants were tested on untrained members of the category to assess generalization. Familiarization and testing was completed 2 additional times. Only participants in the high-variability group showed evidence of learning after an initial period of familiarization. Participants in the high-repetition group were able to learn after additional input. Both groups benefited when words included 2 cues to gender compared to a single cue. The results demonstrate that the degree of input variability can influence learners' ability to generalize a grammatical subcategory (noun gender) from a natural language. In addition, the presence of multiple cues to linguistic subcategory facilitated learning independent of variability condition.

Continuous operation of four-state continuous-variable quantum key distribution system

NASA Astrophysics Data System (ADS)

Matsubara, Takuto; Ono, Motoharu; Oguri, Yusuke; Ichikawa, Tsubasa; Hirano, Takuya; Kasai, Kenta; Matsumoto, Ryutaroh; Tsurumaru, Toyohiro

2016-10-01

We report on the development of continuous-variable quantum key distribution (CV-QKD) system that are based on discrete quadrature amplitude modulation (QAM) and homodyne detection of coherent states of light. We use a pulsed light source whose wavelength is 1550 nm and repetition rate is 10 MHz. The CV-QKD system can continuously generate secret key which is secure against entangling cloner attack. Key generation rate is 50 kbps when the quantum channel is a 10 km optical fiber. The CV-QKD system we have developed utilizes the four-state and post-selection protocol [T. Hirano, et al., Phys. Rev. A 68, 042331 (2003).]; Alice randomly sends one of four states {|+/-α⟩,|+/-𝑖α⟩}, and Bob randomly performs x- or p- measurement by homodyne detection. A commercially available balanced receiver is used to realize shot-noise-limited pulsed homodyne detection. GPU cards are used to accelerate the software-based post-processing. We use a non-binary LDPC code for error correction (reverse reconciliation) and the Toeplitz matrix multiplication for privacy amplification.

Transient impact of prolonged versus repetitive stretch on hand motor control in chronic stroke.

PubMed

Triandafilou, Kristen M; Ochoa, Jose; Kang, Xuan; Fischer, Heidi C; Stoykov, Mary Ellen; Kamper, Derek G

2011-01-01

The purpose of this study was to investigate the influence of prolonged and repetitive passive range of motion (PROM) stretching of the fingers on hand function in stroke survivors. Fifteen chronic stroke survivors with moderate to severe hand impairment took part in the study. Participants underwent 3 experimental sessions consisting of 30 minutes of rest, prolonged, or repetitive stretching of the finger flexor muscles by a powered glove orthosis (X-Glove). Outcome measures, comprised of 3 selected tasks from the Graded Wolf Motor Function Test (GWMFT), grip strength, lateral pinch strength, and grip relaxation time, were recorded at the start and end of each session. Change in outcome score for each session was used for analysis. Data suggested a trend for improvement following stretching, especially for the repetitive PROM case. For one GWMFT task (lift washcloth), the effect of stretching condition on performance time approached a statistical significance (P = .015), with repetitive PROM stretching producing the greatest mean reduction. Similarly, repetitive stretching led to a 12% ± 16% increase in grip strength, although this change was not statistically different across groups (P = .356); and grip termination time was reduced, albeit non-significantly, by 66% ± 133%. Repetitive PROM stretching exhibited trends to be more effective than prolonged stretching for improving hand motor control. Although the results were highly variable and the effects are undoubtedly transient, an extended period of repetitive PROM stretching may prove advantageous prior to hand therapy sessions to maximize treatment.

Facilitation and interference in naming: A consequence of the same learning process?

PubMed

Hughes, Julie W; Schnur, Tatiana T

2017-08-01

Our success with naming depends on what we have named previously, a phenomenon thought to reflect learning processes. Repeatedly producing the same name facilitates language production (i.e., repetition priming), whereas producing semantically related names hinders subsequent performance (i.e., semantic interference). Semantic interference is found whether naming categorically related items once (continuous naming) or multiple times (blocked cyclic naming). A computational model suggests that the same learning mechanism responsible for facilitation in repetition creates semantic interference in categorical naming (Oppenheim, Dell, & Schwartz, 2010). Accordingly, we tested the predictions that variability in semantic interference is correlated across categorical naming tasks and is caused by learning, as measured by two repetition priming tasks (picture-picture repetition priming, Exp. 1; definition-picture repetition priming, Exp. 2, e.g., Wheeldon & Monsell, 1992). In Experiment 1 (77 subjects) semantic interference and repetition priming effects were robust, but the results revealed no relationship between semantic interference effects across contexts. Critically, learning (picture-picture repetition priming) did not predict semantic interference effects in either task. We replicated these results in Experiment 2 (81 subjects), finding no relationship between semantic interference effects across tasks or between semantic interference effects and learning (definition-picture repetition priming). We conclude that the changes underlying facilitatory and interfering effects inherent to lexical access are the result of distinct learning processes where multiple mechanisms contribute to semantic interference in naming. Copyright © 2017 Elsevier B.V. All rights reserved.

The Effects of Ballistic and Non-Ballistic Bench Press on Mechanical Variables.

PubMed

Moir, Gavin L; Munford, Shawn N; Moroski, Lindsey L; Davis, Shala E

2017-02-21

To investigate the effects of ballistic and non-ballistic bench press performed with loads equivalent to 30 and 90% 1-repetition maximum (1-RM) on mechanical variables. Eleven resistance-trained men (age: 23.0 ± 1.4 years; mass: 98.4 ± 14.4 kg) attended four testing sessions where they performed one of the following sessions: 1) three sets of five non-ballistic repetitions performed with a load equivalent to 30% 1-RM (30N-B), 2) three sets of five ballistic repetitions performed with a load equivalent to 30% 1-RM (30B), 3) three sets of four non-ballistic repetitions with a load equivalent to 90% 1-RM (90N-B), 4) three sets of four ballistic repetitions with a load equivalent to 90% 1-RM (90B). Force plates and a 3-D motion analysis system were used to determine the velocity, force, power output (PO) and work during each repetition. The heavier loads resulted in significantly greater forces applied to the barbell (mean differences: 472-783 N, p<0.001), but lower barbell velocities (mean differences: 0.85-1.20 m/s, p<0.001) and PO (mean differences: 118-492 W, p≤0.022). The ballistic conditions enhanced the mechanical variables only at the lower load with 30B producing significantly greater force (mean difference: 263 N, p<0.001), velocity (mean difference: 0.33 m/s, p<0.001), and PO (mean difference: 335 W, p<0.001) compared to 30N-B. Furthermore, the increase in PO across the 3 sets in 30B was significantly different from all other conditions (p=0.013). The total mechanical work performed was significantly greater for the conditions with the heavier loads compared to those with the lighter loads (mean differences: 3,62-5,600 J, p<0.001) and that performed during the ballistic conditions was significantly greater than that performed during the non-ballistic conditions with the same load (mean differences: 945-1,030 J, p<0.001). Ballistic bench press may be an effective exercise for developing power output and multiple sets may elicit post-activation potentiation that enhances force production. However, these benefits may be negated at heavier loads.

Genome-wide analysis of LTR-retrotransposon diversity and its impact on the evolution of the genus Helianthus (L.).

PubMed

Mascagni, Flavia; Giordani, Tommaso; Ceccarelli, Marilena; Cavallini, Andrea; Natali, Lucia

2017-08-18

Genome divergence by mobile elements activity and recombination is a continuous process that plays a key role in the evolution of species. Nevertheless, knowledge on retrotransposon-related variability among species belonging to the same genus is still limited. Considering the importance of the genus Helianthus, a model system for studying the ecological genetics of speciation and adaptation, we performed a comparative analysis of the repetitive genome fraction across ten species and one subspecies of sunflower, focusing on long terminal repeat retrotransposons at superfamily, lineage and sublineage levels. After determining the relative genome size of each species, genomic DNA was isolated and subjected to Illumina sequencing. Then, different assembling and clustering approaches allowed exploring the repetitive component of all genomes. On average, repetitive DNA in Helianthus species represented more than 75% of the genome, being composed mostly by long terminal repeat retrotransposons. Also, the prevalence of Gypsy over Copia superfamily was observed and, among lineages, Chromovirus was by far the most represented. Although nearly all the same sublineages are present in all species, we found considerable variability in the abundance of diverse retrotransposon lineages and sublineages, especially between annual and perennial species. This large variability should indicate that different events of amplification or loss related to these elements occurred following species separation and should have been involved in species differentiation. Our data allowed us inferring on the extent of interspecific repetitive DNA variation related to LTR-RE abundance, investigating the relationship between changes of LTR-RE abundance and the evolution of the genus, and determining the degree of coevolution of different LTR-RE lineages or sublineages between and within species. Moreover, the data suggested that LTR-RE abundance in a species was affected by the annual or perennial habit of that species.

Quantitative characterization of color Doppler images: reproducibility, accuracy, and limitations.

PubMed

Delorme, S; Weisser, G; Zuna, I; Fein, M; Lorenz, A; van Kaick, G

1995-01-01

A computer-based quantitative analysis for color Doppler images of complex vascular formations is presented. The red-green-blue-signal from an Acuson XP10 is frame-grabbed and digitized. By matching each image pixel with the color bar, color pixels are identified and assigned to the corresponding flow velocity (color value). Data analysis consists of delineation of a region of interest and calculation of the relative number of color pixels in this region (color pixel density) as well as the mean color value. The mean color value was compared to flow velocities in a flow phantom. The thyroid and carotid artery in a volunteer were repeatedly examined by a single examiner to assess intra-observer variability. The thyroids in five healthy controls were examined by three experienced physicians to assess the extent of inter-observer variability and observer bias. The correlation between the mean color value and flow velocity ranged from 0.94 to 0.96 for a range of velocities determined by pulse repetition frequency. The average deviation of the mean color value from the flow velocity was 22% to 41%, depending on the selected pulse repetition frequency (range of deviations, -46% to +66%). Flow velocity was underestimated with inadequately low pulse repetition frequency, or inadequately high reject threshold. An overestimation occurred with inadequately high pulse repetition frequency. The highest intra-observer variability was 22% (relative standard deviation) for the color pixel density, and 9.1% for the mean color value. The inter-observer variation was approximately 30% for the color pixel density, and 20% for the mean color value. In conclusion, computer assisted image analysis permits an objective description of color Doppler images. However, the user must be aware that image acquisition under in vivo conditions as well as physical and instrumental factors may considerably influence the results.

Energy-density and repetition-rate dependences of the KrF-excimer-laser-induced 1.9-eV emission band in type-III fused silicas

NASA Astrophysics Data System (ADS)

Kuzuu, Nobu; Komatsu, Yoshikazu; Murahara, Masataka

1993-02-01

The energy-density and repetition-rate dependences of the intensity of KrF-excimer-laser (5.0 eV) -induced 1.9-eV emission band in type-III fused silicas synthesized under different conditions were investigated. The intensity of the 1.9-eV band is proportional to the 1.7-th power of the energy density and the 0.6-th power of the repetition rate of the laser pulse. The origin of these dependencies was discussed based on the trapped-oxygen-molecule model proposed by Awazu and Kawazoe; by irradiating with the excimer laser, ozone molecules are formed from dissolved oxygen molecules and 1.9-eV photons are emitted in the course of the photodecomposition of the ozone molecules. Therefore, a two-step photon-absorption process is needed to emit the 1.9-eV photon. To form the ozone molecule, diffusion of the oxygen atoms produced by the photodecomposition of the trapped oxygen molecules are needed. This model suggests that the intensity of the 1.9-eV band is proportional to the square of the energy density and the square root of the repetition rate; this dependency is nearly the same as that of our experimental result.

Repeated change-of-direction test for collegiate male soccer players.

PubMed

Mizuguchi, S; Gray, H; Calabrese, L S; Haff, G G; Sands, W A; Ramsey, M W; Cardinale, M; Stone, M H

2014-08-01

The aim of the study was to investigate the applicability of a repeated change-of-direction (RCoD) test for NCAA Division-I male soccer players. The RCoD test consisted of 5 diagonal direction changes per repetition with a soccer ball to be struck at the end. Each player performed 15 repetitions with approximately 10 seconds to jog back between repetitions. Data were collected in two sessions. In the first session, 13 players were examined for heart rate responses and blood lactate concentrations. In the second session, 22 players were examined for the test's ability to discriminate the primary from secondary players (78.0±16.1 and 10.4±13.3 minutes per match, respectively). Heart rate data were available only from 9 players due to artifacts. The peak heart rate (200.2±6.6 beats∙min-1: 99.9±3.0% maximum) and blood lactate concentration (14.8±2.4 mmol∙L-1 immediately after) resulted in approximately 3.5 and 6.4-fold increases from the resting values, respectively. These values appear comparable to those during intense periods of soccer matches. In addition, the average repetition time of the test was found to discriminate the primary (4.85±0.23 s) from the secondary players (5.10±0.24 s) (P=0.02). The RCoD test appears to induce physiological responses similar to intense periods of soccer matches with respect to heart rate and blood lactate concentration. Players with better average repetition times tend to be those who play major minutes.

Architecture for a 1-GHz Digital RADAR

NASA Technical Reports Server (NTRS)

Mallik, Udayan

2011-01-01

An architecture for a Direct RF-digitization Type Digital Mode RADAR was developed at GSFC in 2008. Two variations of a basic architecture were developed for use on RADAR imaging missions using aircraft and spacecraft. Both systems can operate with a pulse repetition rate up to 10 MHz with 8 received RF samples per pulse repetition interval, or at up to 19 kHz with 4K received RF samples per pulse repetition interval. The first design describes a computer architecture for a Continuous Mode RADAR transceiver with a real-time signal processing and display architecture. The architecture can operate at a high pulse repetition rate without interruption for an infinite amount of time. The second design describes a smaller and less costly burst mode RADAR that can transceive high pulse repetition rate RF signals without interruption for up to 37 seconds. The burst-mode RADAR was designed to operate on an off-line signal processing paradigm. The temporal distribution of RF samples acquired and reported to the RADAR processor remains uniform and free of distortion in both proposed architectures. The majority of the RADAR's electronics is implemented in digital CMOS (complementary metal oxide semiconductor), and analog circuits are restricted to signal amplification operations and analog to digital conversion. An implementation of the proposed systems will create a 1-GHz, Direct RF-digitization Type, L-Band Digital RADAR--the highest band achievable for Nyquist Rate, Direct RF-digitization Systems that do not implement an electronic IF downsample stage (after the receiver signal amplification stage), using commercially available off-the-shelf integrated circuits.

Proposal of a Consensus Set of Hypervariable Mycobacterial Interspersed Repetitive-Unit–Variable-Number Tandem-Repeat Loci for Subtyping of Mycobacterium tuberculosis Beijing Isolates

PubMed Central

Allix-Béguec, Caroline; Wahl, Céline; Hanekom, Madeleine; Nikolayevskyy, Vladyslav; Drobniewski, Francis; Maeda, Shinji; Campos-Herrero, Isolina; Mokrousov, Igor; Niemann, Stefan; Kontsevaya, Irina; Rastogi, Nalin; Samper, Sofia; Sng, Li-Hwei; Warren, Robin M.

2014-01-01

Mycobacterium tuberculosis Beijing strains represent targets of special importance for molecular surveillance of tuberculosis (TB), especially because they are associated with spread of multidrug resistance in some world regions. Standard 24-locus mycobacterial interspersed repetitive-unit–variable-number tandem-repeat (MIRU-VNTR) typing lacks resolution power for accurately discriminating closely related clones that often compose Beijing strain populations. Therefore, we evaluated a set of 7 additional, hypervariable MIRU-VNTR loci for better resolution and tracing of such strains, using a collection of 535 Beijing isolates from six world regions where these strains are known to be prevalent. The typeability and interlaboratory reproducibility of these hypervariable loci were lower than those of the 24 standard loci. Three loci (2163a, 3155, and 3336) were excluded because of their redundant variability and/or more frequent noninterpretable results compared to the 4 other markers. The use of the remaining 4-locus set (1982, 3232, 3820, and 4120) increased the number of types by 52% (from 223 to 340) and reduced the clustering rate from 58.3 to 36.6%, when combined with the use of the standard 24-locus set. Known major clonal complexes/24-locus-based clusters were all subdivided, although the degree of subdivision varied depending on the complex. Only five single-locus variations were detected among the hypervariable loci of an additional panel of 92 isolates, representing 15 years of clonal spread of a single Beijing strain in a geographically restricted setting. On this calibrated basis, we propose this 4-locus set as a consensus for subtyping Beijing clonal complexes and clusters, after standard typing. PMID:24172154

Proposal of a consensus set of hypervariable mycobacterial interspersed repetitive-unit-variable-number tandem-repeat loci for subtyping of Mycobacterium tuberculosis Beijing isolates.

PubMed

Allix-Béguec, Caroline; Wahl, Céline; Hanekom, Madeleine; Nikolayevskyy, Vladyslav; Drobniewski, Francis; Maeda, Shinji; Campos-Herrero, Isolina; Mokrousov, Igor; Niemann, Stefan; Kontsevaya, Irina; Rastogi, Nalin; Samper, Sofia; Sng, Li-Hwei; Warren, Robin M; Supply, Philip

2014-01-01

Mycobacterium tuberculosis Beijing strains represent targets of special importance for molecular surveillance of tuberculosis (TB), especially because they are associated with spread of multidrug resistance in some world regions. Standard 24-locus mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing lacks resolution power for accurately discriminating closely related clones that often compose Beijing strain populations. Therefore, we evaluated a set of 7 additional, hypervariable MIRU-VNTR loci for better resolution and tracing of such strains, using a collection of 535 Beijing isolates from six world regions where these strains are known to be prevalent. The typeability and interlaboratory reproducibility of these hypervariable loci were lower than those of the 24 standard loci. Three loci (2163a, 3155, and 3336) were excluded because of their redundant variability and/or more frequent noninterpretable results compared to the 4 other markers. The use of the remaining 4-locus set (1982, 3232, 3820, and 4120) increased the number of types by 52% (from 223 to 340) and reduced the clustering rate from 58.3 to 36.6%, when combined with the use of the standard 24-locus set. Known major clonal complexes/24-locus-based clusters were all subdivided, although the degree of subdivision varied depending on the complex. Only five single-locus variations were detected among the hypervariable loci of an additional panel of 92 isolates, representing 15 years of clonal spread of a single Beijing strain in a geographically restricted setting. On this calibrated basis, we propose this 4-locus set as a consensus for subtyping Beijing clonal complexes and clusters, after standard typing.

Novel Mechanism for Reducing Acute and Chronic Neurodegeneration After Traumatic Brain Injury

DTIC Science & Technology

2017-07-01

glutamate from the brain. Scope: We will test this novel and powerful neuroprotective treatment in a rat model of repetitive mild (concussive) TBIs...variability. 2. Completed statistical analysis of behavioral experiments examining effects of rGOT and rGOT + OxAc on outcome on rotarod and Morris water ...neuroprotective treatment in a rat model of a single moderate TBI and in a rat model of repetitive mild (concussive) TBIs. Outcome measures include blood and

Application of a symbolic motion structure representation algorithm to identify upper extremity kinematic changes during a repetitive task.

PubMed

Whittaker, Rachel L; Park, Woojin; Dickerson, Clark R

2018-04-27

Efficient and holistic identification of fatigue-induced movement strategies can be limited by large between-subject variability in descriptors of joint angle data. One promising alternative to traditional, or computationally intensive methods is the symbolic motion structure representation algorithm (SMSR), which identifies the basic spatial-temporal structure of joint angle data using string descriptors of temporal joint angle trajectories. This study attempted to use the SMSR to identify changes in upper extremity time series joint angle data during a repetitive goal directed task causing muscle fatigue. Twenty-eight participants (15 M, 13 F) performed a seated repetitive task until fatigued. Upper extremity joint angles were extracted from motion capture for representative task cycles. SMSRs, averages and ranges of several joint angles were compared at the start and end of the repetitive task to identify kinematic changes with fatigue. At the group level, significant increases in the range of all joint angle data existed with large between-subject variability that posed a challenge to the interpretation of these fatigue-related changes. However, changes in the SMSRs across participants effectively summarized the adoption of adaptive movement strategies. This establishes SMSR as a viable, logical, and sensitive method of fatigue identification via kinematic changes, with novel application and pragmatism for visual assessment of fatigue development. Copyright © 2018 Elsevier Ltd. All rights reserved.

Phonological neighborhood and word frequency effects on the stuttered disfluencies of children who stutter: comments on Anderson (2007).

PubMed

Howell, Peter

2010-10-01

This letter comments on a study by Anderson (2007) that compared the effects of word frequency, neighborhood density, and phonological neighborhood frequency on part-word repetitions, prolongations, and single-syllable word repetitions produced by children who stutter. Anderson discussed her results with respect to 2 theories about stuttering: the covert repair hypothesis and execution planning (EXPLAN) theory. Her remarks about EXPLAN theory are examined. Anderson considered that EXPLAN does not predict the relationship between word and neighborhood frequency and stuttering for part-word repetitions and prolongations (she considered that EXPLAN predicts that stuttering occurs on simple words for children). The actual predictions that EXPLAN makes are upheld by her results. She also considered that EXPLAN cannot account for why stuttering is affected by the same variables that lead to speech errors, and it is shown that this is incorrect. The effects of word frequency, neighborhood density, and phonological neighborhood frequency on part-word repetitions, prolongations, and single-syllable word repetitions reported by Anderson (2007) are consistent with the predictions of the EXPLAN model.

Repetitive flood victims and acceptance of FEMA mitigation offers: an analysis with community-system policy implications.

PubMed

Kick, Edward L; Fraser, James C; Fulkerson, Gregory M; McKinney, Laura A; De Vries, Daniel H

2011-07-01

Of all natural disasters, flooding causes the greatest amount of economic and social damage. The United States' Federal Emergency Management Agency (FEMA) uses a number of hazard mitigation grant programmes for flood victims, including mitigation offers to relocate permanently repetitive flood loss victims. This study examines factors that help to explain the degree of difficulty repetitive flood loss victims experience when they make decisions about relocating permanently after multiple flood losses. Data are drawn from interviews with FEMA officials and a survey of flood victims from eight repetitive flooding sites. The qualitative and quantitative results show the importance of rational choices by flood victims in their mitigation decisions, as they relate to financial variables, perceptions of future risk, attachments to home and community, and the relationships between repetitive flood loss victims and the local flood management officials who help them. The results offer evidence to suggest the value of a more community-system approach to FEMA relocation practices. © 2011 The Author(s). Disasters © Overseas Development Institute, 2011.

Modeling of a latent fault detector in a digital system

NASA Technical Reports Server (NTRS)

Nagel, P. M.

1978-01-01

Methods of modeling the detection time or latency period of a hardware fault in a digital system are proposed that explain how a computer detects faults in a computational mode. The objectives were to study how software reacts to a fault, to account for as many variables as possible affecting detection and to forecast a given program's detecting ability prior to computation. A series of experiments were conducted on a small emulated microprocessor with fault injection capability. Results indicate that the detecting capability of a program largely depends on the instruction subset used during computation and the frequency of its use and has little direct dependence on such variables as fault mode, number set, degree of branching and program length. A model is discussed which employs an analog with balls in an urn to explain the rate of which subsequent repetitions of an instruction or instruction set detect a given fault.

Actively Q-switched, thulium-holmium-codoped fiber laser incorporating a silicon-based, variable-optical-attenuator-based Q switch.

PubMed

Jung, Minwan; Han Lee, Ju

2013-04-20

An actively Q-switched thulium-holmium-codoped fiber laser incorporating an Si-based variable optical attenuator (VOA) is experimentally demonstrated. It has been shown that an Si-based VOA with a response time of hundreds of nanoseconds can be used as a cost-effective 2 μm Q switch due to its extremely wide operating bandwidth from 1.5 to 2 μm, and low electrical power consumption. In our study, the laser's slope efficiency was measured to be ~17% at an operating wavelength of 1.89 μm. The repetition rate tuning range was from 20 to 80 kHz, which was limited by the optical damage threshold and the response time. The minimum temporal pulsewidth was measured to be ~184 ns at a modulation frequency of 20 kHz, and the corresponding maximum peak power was ~10 W.

Actigraphy in Patients With Major Depressive Disorder Undergoing Repetitive Transcranial Magnetic Stimulation: An Open Label Pilot Study.

PubMed

Nishida, Masaki; Kikuchi, Senichiro; Nisijima, Koichi; Suda, Shiro

2017-03-01

The effects of repetitive transcranial magnetic stimulation (rTMS) on physical activity and sleep patterns in individuals with major depressive disorder (MDD) remain unclear. We examined the effects of rTMS treatment on the rest-activity cycle and sleep disturbances in MDD. In this open-label pilot study, 14 patients with medication-resistant MDD underwent 10 rTMS sessions over the bilateral dorsolateral prefrontal cortex. In addition to Hamilton Depression Rating Scale and Pittsburgh Sleep Quality Index scores, waist actigraphy was used to evaluate alterations in the rest-activity cycle over the course of rTMS treatments. Actigraphic data were evaluated at baseline and in the first (rTMS sessions 1-3), second (rTMS sessions 4-7), and third (rTMS sessions 8-10) sections. Although Hamilton Depression Rating Scale and Pittsburgh Sleep Quality Index scores were significantly improved by rTMS, sleep variables assessed by actigraphy did not show significant changes. However, post hoc tests indicated a significant increase in mean steps per day between the baseline and first section time points (P = 0.014; t13 = -2.316). Our data indicated that a daytime physical activity response to rTMS occurred in early sessions, whereas subjective symptom improvements were consistent across all sessions. Future double-blind placebo-controlled studies assessing the effects of rTMS on the rest-activity cycle and sleep disturbances in MDD are warranted.

Substantial Regional Variation in Substitution Rates in the Human Genome: Importance of GC Content, Gene Density, and Telomere-Specific Effects

NASA Astrophysics Data System (ADS)

Arndt, Peter F.; Hwa, Terence; Petrov, Dmitri A.

2005-06-01

This study presents the first global, 1 Mbp level analysis of patterns of nucleotide substitutions along the human lineage. The study is based on the analysis of a large amount of repetitive elements deposited into the human genome since the mammalian radiation, yielding a number of results that would have been difficult to obtain using the more conventional comparative method of analysis. This analysis revealed substantial and consistent variability of rates of substitution, with the variability ranging up to 2-fold among different regions. The rates of substitutions of C or G nucleotides with A or T nucleotides vary much more sharply than the reverse rates suggesting that much of that variation is due to differences in mutation rates rather than in the probabilities of fixation of C/G vs. A/T nucleotides across the genome. For all types of substitution we observe substantially more hotspots than coldspots, with hotspots showing substantial clustering over tens of Mbp's. Our analysis revealed that GC-content of surrounding sequences is the best predictor of the rates of substitution. The pattern of substitution appears very different near telomeres compared to the rest of the genome and cannot be explained by the genome-wide correlations of the substitution rates with GC content or exon density. The telomere pattern of substitution is consistent with natural selection or biased gene conversion acting to increase the GC-content of the sequences that are within 10-15 Mbp away from the telomere.

Entropy measures detect increased movement variability in resistance training when elite rugby players use the ball.

PubMed

Moras, Gerard; Fernández-Valdés, Bruno; Vázquez-Guerrero, Jairo; Tous-Fajardo, Julio; Exel, Juliana; Sampaio, Jaime

2018-05-24

This study described the variability in acceleration during a resistance training task, performed in horizontal inertial flywheels without (NOBALL) or with the constraint of catching and throwing a rugby ball (BALL). Twelve elite rugby players (mean±SD: age 25.6±3.0years, height 1.82±0.07m, weight 94.0±9.9kg) performed a resistance training task in both conditions (NOBALL AND BALL). Players had five minutes of a standardized warm-up, followed by two series of six repetitions of both conditions: at the first three repetitions the intensity was progressively increased while the last three were performed at maximal voluntary effort. Thereafter, the participants performed two series of eight repetitions from each condition for two days and in a random order, with a minimum of 10min between series. The structure of variability was analysed using non-linear measures of entropy. Mean changes (%; ±90% CL) of 4.64; ±3.1g for mean acceleration and 39.48; ±36.63a.u. for sample entropy indicated likely and very likely increase when in BALL condition. Multiscale entropy also showed higher unpredictability of acceleration under the BALL condition, especially at higher time scales. The application of match specific constraints in resistance training for rugby players elicit different amount of variability of body acceleration across multiple physiological time scales. Understanding the non-linear process inherent to the manipulation of resistance training variables with constraints and its motor adaptations may help coaches and trainers to enhance the effectiveness of physical training and, ultimately, better understand and maximize sports performance. Copyright © 2018 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

High Repetition Rate Pulsed 2-Micron Laser Transmitter for Coherent CO2 DIAL Measurement

NASA Technical Reports Server (NTRS)

Singh, Uprendra N.; Bai, Yingxin; Yu, Jirong; Petros, Mulugeta; Petzar, Paul J.; Trieu, Bo C.; Lee, Hyung

2009-01-01

A high repetition rate, highly efficient, Q-switched 2-micron laser system as the transmitter of a coherent differential absorption lidar for CO2 measurement has been developed at NASA Langley Research Center. Such a laser transmitter is a master-slave laser system. The master laser operates in a single frequency, either on-line or off-line of a selected CO2 absorption line. The slave laser is a Q-switched ring-cavity Ho:YLF laser which is pumped by a Tm:fiber laser. The repetition rate can be adjusted from a few hundred Hz to 10 kHz. The injection seeding success rate is from 99.4% to 99.95%. For 1 kHz operation, the output pulse energy is 5.5mJ with the pulse length of approximately 50 ns. The optical-to-optical efficiency is 39% when the pump power is 14.5W. The measured standard deviation of the laser frequency jitter is about 3 MHz.

Delay induced high order locking effects in semiconductor lasers

NASA Astrophysics Data System (ADS)

Kelleher, B.; Wishon, M. J.; Locquet, A.; Goulding, D.; Tykalewicz, B.; Huyet, G.; Viktorov, E. A.

2017-11-01

Multiple time scales appear in many nonlinear dynamical systems. Semiconductor lasers, in particular, provide a fertile testing ground for multiple time scale dynamics. For solitary semiconductor lasers, the two fundamental time scales are the cavity repetition rate and the relaxation oscillation frequency which is a characteristic of the field-matter interaction in the cavity. Typically, these two time scales are of very different orders, and mutual resonances do not occur. Optical feedback endows the system with a third time scale: the external cavity repetition rate. This is typically much longer than the device cavity repetition rate and suggests the possibility of resonances with the relaxation oscillations. We show that for lasers with highly damped relaxation oscillations, such resonances can be obtained and lead to spontaneous mode-locking. Two different laser types-—a quantum dot based device and a quantum well based device—are analysed experimentally yielding qualitatively identical dynamics. A rate equation model is also employed showing an excellent agreement with the experimental results.

Delay induced high order locking effects in semiconductor lasers.

PubMed

Kelleher, B; Wishon, M J; Locquet, A; Goulding, D; Tykalewicz, B; Huyet, G; Viktorov, E A

2017-11-01

Multiple time scales appear in many nonlinear dynamical systems. Semiconductor lasers, in particular, provide a fertile testing ground for multiple time scale dynamics. For solitary semiconductor lasers, the two fundamental time scales are the cavity repetition rate and the relaxation oscillation frequency which is a characteristic of the field-matter interaction in the cavity. Typically, these two time scales are of very different orders, and mutual resonances do not occur. Optical feedback endows the system with a third time scale: the external cavity repetition rate. This is typically much longer than the device cavity repetition rate and suggests the possibility of resonances with the relaxation oscillations. We show that for lasers with highly damped relaxation oscillations, such resonances can be obtained and lead to spontaneous mode-locking. Two different laser types--a quantum dot based device and a quantum well based device-are analysed experimentally yielding qualitatively identical dynamics. A rate equation model is also employed showing an excellent agreement with the experimental results.

Sub-20-ps pulses from a passively Q-switched microchip laser at 1  MHz repetition rate.

PubMed

Mehner, Eva; Bernard, Benjamin; Giessen, Harald; Kopf, Daniel; Braun, Bernd

2014-05-15

We present a 50 μm Nd3+:YVO4 microchip laser that is passively Q-switched by a semiconductor saturable absorber mirror. To reduce handling problems caused by the small crystal dimensions, the 50 μm Nd3+:YVO4 crystal is optically bonded to an undoped YVO4 crystal of a length of about 500 μm. By using a saturable absorber mirror with an effective modulation depth of >10% the system is able to deliver 16 ps pulses at a repetition rate of up to 1.0 MHz. The average laser power is 16 mW at 1064 nm. To our knowledge these are the shortest Q-switched pulses ever reported from a solid-state laser. The limits in terms of pulse width, repetition rate, output power, and system stability are discussed. Additionally, continuous-wave behavior is analyzed. Experimental data is compared with the simulation results of the coupled rate equations.

Multiphoton lithography using a high-repetition rate microchip laser.

PubMed

Ritschdorff, Eric T; Shear, Jason B

2010-10-15

Multiphoton lithography (MPL) provides a means to create prototype, three-dimensional (3D) materials for numerous applications in analysis and cell biology. A major impediment to the broad adoption of MPL in research laboratories is its reliance on high peak-power light sources, a requirement that typically has been met using expensive femtosecond titanium:sapphire lasers. Development of affordable microchip laser sources has the potential to substantially extend the reach of MPL, but previous lasers have provided relatively low pulse repetition rates (low kilohertz range), thereby limiting the rate at which microforms could be produced using this direct-write approach. In this report, we examine the MPL capabilities of a new, high-repetition-rate (36.6 kHz) microchip Nd:YAG laser. We show that this laser enables an approximate 4-fold decrease in fabrication times for protein-based microforms relative to the existing state-of-the-art microchip source and demonstrate its utility for creating complex 3D microarchitectures.

1.55 µm InAs/GaAs Quantum Dots and High Repetition Rate Quantum Dot SESAM Mode-locked Laser

NASA Astrophysics Data System (ADS)

Zhang, Z. Y.; Oehler, A. E. H.; Resan, B.; Kurmulis, S.; Zhou, K. J.; Wang, Q.; Mangold, M.; Süedmeyer, T.; Keller, U.; Weingarten, K. J.; Hogg, R. A.

2012-06-01

High pulse repetition rate (>=10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.55 µm In(Ga)As QDs on GaAs substrates, their incorporation into a SESAM, and the realization of the first 10 GHz repetition rate QD-SESAM modelocked laser at 1.55 µm, exhibiting ~2 ps pulse width from an Er-doped glass oscillator (ERGO). With a high areal dot density and strong light emission, this QD structure is a very promising candidate for many other applications, such as laser diodes, optical amplifiers, non-linear and photonic crystal based devices.

Complete analog control of the carrier-envelope-phase of a high-power laser amplifier.

PubMed

Feng, C; Hergott, J-F; Paul, P-M; Chen, X; Tcherbakoff, O; Comte, M; Gobert, O; Reduzzi, M; Calegari, F; Manzoni, C; Nisoli, M; Sansone, G

2013-10-21

In this work we demonstrate the development of a complete analog feedback loop for the control of the carrier-envelope phase (CEP) of a high-average power (20 W) laser operating at 10 kHz repetition rate. The proposed method combines a detection scheme working on a single-shot basis at the full-repetition-rate of the laser system with a fast actuator based either on an acousto-optic or on an electro-optic crystal. The feedback loop is used to correct the CEP fluctuations introduced by the amplification process demonstrating a CEP residual noise of 320 mrad measured on a single-shot basis. The comparison with a feedback loop operating at a lower sampling rate indicates an improvement up to 45% in the residual noise. The measurement of the CEP drift for different integration times clearly evidences the importance of the single-shot characterization of the residual CEP drift. The demonstrated scheme could be efficiently applied for systems approaching the 100 kHz repetition rate regime.

Development of a picosecond CO2 laser system for a high-repetition γ-source

NASA Astrophysics Data System (ADS)

Polyanskiy, Mikhail N.; Pogorelsky, Igor V.; Yakimenko, Vitaly E.; Platonenko, Victor T.

2008-10-01

The concept of a high-repetition-rate, high-average power γ-source is based on Compton backscattering from the relativistic electron beam inside a picosecond CO2 laser cavity. Proof-of-principle experiments combined with comput

Repetitive patterns in rapid optical variations in the nearby black-hole binary V404 Cygni.

PubMed

Kimura, Mariko; Isogai, Keisuke; Kato, Taichi; Ueda, Yoshihiro; Nakahira, Satoshi; Shidatsu, Megumi; Enoto, Teruaki; Hori, Takafumi; Nogami, Daisaku; Littlefield, Colin; Ishioka, Ryoko; Chen, Ying-Tung; King, Sun-Kun; Wen, Chih-Yi; Wang, Shiang-Yu; Lehner, Matthew J; Schwamb, Megan E; Wang, Jen-Hung; Zhang, Zhi-Wei; Alcock, Charles; Axelrod, Tim; Bianco, Federica B; Byun, Yong-Ik; Chen, Wen-Ping; Cook, Kem H; Kim, Dae-Won; Lee, Typhoon; Marshall, Stuart L; Pavlenko, Elena P; Antonyuk, Oksana I; Antonyuk, Kirill A; Pit, Nikolai V; Sosnovskij, Aleksei A; Babina, Julia V; Baklanov, Aleksei V; Pozanenko, Alexei S; Mazaeva, Elena D; Schmalz, Sergei E; Reva, Inna V; Belan, Sergei P; Inasaridze, Raguli Ya; Tungalag, Namkhai; Volnova, Alina A; Molotov, Igor E; de Miguel, Enrique; Kasai, Kiyoshi; Stein, William L; Dubovsky, Pavol A; Kiyota, Seiichiro; Miller, Ian; Richmond, Michael; Goff, William; Andreev, Maksim V; Takahashi, Hiromitsu; Kojiguchi, Naoto; Sugiura, Yuki; Takeda, Nao; Yamada, Eiji; Matsumoto, Katsura; James, Nick; Pickard, Roger D; Tordai, Tamás; Maeda, Yutaka; Ruiz, Javier; Miyashita, Atsushi; Cook, Lewis M; Imada, Akira; Uemura, Makoto

2016-01-07

How black holes accrete surrounding matter is a fundamental yet unsolved question in astrophysics. It is generally believed that matter is absorbed into black holes via accretion disks, the state of which depends primarily on the mass-accretion rate. When this rate approaches the critical rate (the Eddington limit), thermal instability is supposed to occur in the inner disk, causing repetitive patterns of large-amplitude X-ray variability (oscillations) on timescales of minutes to hours. In fact, such oscillations have been observed only in sources with a high mass-accretion rate, such as GRS 1915+105 (refs 2, 3). These large-amplitude, relatively slow timescale, phenomena are thought to have physical origins distinct from those of X-ray or optical variations with small amplitudes and fast timescales (less than about 10 seconds) often observed in other black-hole binaries-for example, XTE J1118+480 (ref. 4) and GX 339-4 (ref. 5). Here we report an extensive multi-colour optical photometric data set of V404 Cygni, an X-ray transient source containing a black hole of nine solar masses (and a companion star) at a distance of 2.4 kiloparsecs (ref. 8). Our data show that optical oscillations on timescales of 100 seconds to 2.5 hours can occur at mass-accretion rates more than ten times lower than previously thought. This suggests that the accretion rate is not the critical parameter for inducing inner-disk instabilities. Instead, we propose that a long orbital period is a key condition for these large-amplitude oscillations, because the outer part of the large disk in binaries with long orbital periods will have surface densities too low to maintain sustained mass accretion to the inner part of the disk. The lack of sustained accretion--not the actual rate--would then be the critical factor causing large-amplitude oscillations in long-period systems.

A four kHz repetition rate compact TEA CO2 laser

NASA Astrophysics Data System (ADS)

Zheng, Yijun; Tan, Rongqing

2013-09-01

A compact transversely excited atmospheric (TEA) CO2 laser with high repetition-rate was reported. The size of the laser is 380 mm×300 mm×200 mm, and the discharge volume is 12×103 mm3. The laser cavity has a length of 320mm and consists of a totally reflective concave mirror with a radius of curvature of 4 m (Cu metal substrate coated with Au) and a partially reflecting mirror. The ultraviolet preionization makes the discharge even and stable，the output energy can be as high as 28 mJ under the circumstance of free oscillation, and the width of the light pulse is 60ns．To acquire the high wind velocity, a turbocharger is used in the system of the fast-gas flow cycle. When the wind speed is 100m/s, the repetition rate of the transversely excited atmospheric CO2 laser is up to 2 kHz. On this basis, a dual modular structure with two sets of the gas discharge unit is adopted to obtain a higher pulse repetition frequency output. The dual discharge unit composed two sets of electrodes and two sets of turbo fan. Alternate trigger technology is used to make the two sets of discharge module work in turn with repetition frequency of 2 kHz, the discharge interval of two sets of the gas discharge unit can be adjusted continuously from 20 microseconds to 250 microseconds. Under the conditions of maintaining the other parameters constant, the repetition frequency of the laser pulse is up to 4 kHz. The total size of laser with dual modular structure is 380mm×520mm×200mm, and the discharge volume is 24×103 mm3 with the cavity length of 520mm.

Broadly tunable ultrafast pump-probe system operating at multi-kHz repetition rate

NASA Astrophysics Data System (ADS)

Grupp, Alexander; Budweg, Arne; Fischer, Marco P.; Allerbeck, Jonas; Soavi, Giancarlo; Leitenstorfer, Alfred; Brida, Daniele

2018-01-01

Femtosecond systems based on ytterbium as active medium are ideal for driving ultrafast optical parametric amplifiers in a broad frequency range. The excellent stability of the source and the repetition rate tunable to up to hundreds of kHz allow for the implementation of an advanced two-color pump probe setup with the capability to achieve excellent signal-to-noise performances with sub-10 fs temporal resolution.

Biologically Inspired Waveform Diversity for Synthetic Autonomous Navigation Sensing

DTIC Science & Technology

2009-11-01

Pulse interval and repetition rate When searching for prey, bats often emit one pulse per wing beat . This is because the mechanics of flapping the...wings, breathing, and producing sound pulses are all coupled. Because of this coupling, the pulse repetition rate is often the same as wing beat ...give accurate measures of delay and hence range [26]. For determination of direction, the horizontal angle of a target is determined from binaural

Generating high-peak-power structured lights in selectively pumped passively Q-switched lasers with astigmatic mode transformations

NASA Astrophysics Data System (ADS)

Chang, C. C.; Hsieh, Y. H.; Lee, C. Y.; Sung, C. L.; Tuan, P. H.; Tung, J. C.; Liang, H. C.; Chen, Y. F.

2017-12-01

Various high-order Hermite-Gaussian (HG) modes with high repetition rates and high peak powers are systematically generated by designing the cavity configuration to satisfy the criterion of the passive Q-switching. For the HG m,0 modes with the order m  =  1-9, the pulse repetition rate can exceed 100 kHz with peak power higher than 0.3 kW. For the HG m,m modes with the order m  =  1-10, the pulse repetition rate can be up to 37 kHz with peak power higher than 0.35 kW. Furthermore, the high-order HG beams is transformed by using an astigmatic mode converter to generate various structured lights with optical vortices. Experimental patterns of the transformed high-order HG beams in the propagation are theoretically analyzed and the phase structures are numerically manifested.

X-ray emission as a potential hazard during ultrashort pulse laser material processing

NASA Astrophysics Data System (ADS)

Legall, Herbert; Schwanke, Christoph; Pentzien, Simone; Dittmar, Günter; Bonse, Jörn; Krüger, Jörg

2018-06-01

In laser machining with ultrashort laser pulses unwanted X-ray radiation in the keV range can be generated when a critical laser intensity is exceeded. Even if the emitted X-ray dose per pulse is low, high laser repetition rates can lead to an accumulation of X-ray doses beyond exposure safety limits. For 925 fs pulse duration at a center wavelength of 1030 nm, the X-ray emission was investigated up to an intensity of 2.6 × 1014 W/cm2. The experiments were performed in air with a thin disk laser at a repetition rate of 400 kHz. X-ray spectra and doses were measured for various planar target materials covering a wide range of the periodic table from aluminum to tungsten. Without radiation shielding, the measured radiation doses at this high repetition rate clearly exceed the regulatory limits. Estimations for an adequate radiation shielding are provided.

Morphology of Er:YAG-laser-treated root surfaces

NASA Astrophysics Data System (ADS)

Keller, Ulrich; Stock, Karl; Hibst, Raimund

1997-12-01

From previous studies it could be demonstrated that an efficient ablation of dental calculus is possible using an Er:YAG laser with a special contact fiber tip. After improving of the design and the efficiency of light transmission of the contact tip laser treated tooth root surfaces were investigated due to morphological changes in comparison to conventional root scaling and planing. Surface modifications were observed histologically under the light microscope and by means of a Scanning Electron Microscope. During laser treatment the intrapulpal temperature increase was measured. The results show that the improved contact tip a microstructured surface can be generated, which shows no signs of thermal effects even when a laser pulse repetition rate of 15 Hz was used. Temperature increase was limited to 4 K at a repetition rate of 10 Hz and to 5.5 K at a repetition rate of 15 Hz.

Software defined photon counting system for time resolved x-ray experiments.

PubMed

Acremann, Y; Chembrolu, V; Strachan, J P; Tyliszczak, T; Stöhr, J

2007-01-01

The time structure of synchrotron radiation allows time resolved experiments with sub-100 ps temporal resolution using a pump-probe approach. However, the relaxation time of the samples may require a lower repetition rate of the pump pulse compared to the full repetition rate of the x-ray pulses from the synchrotron. The use of only the x-ray pulse immediately following the pump pulse is not efficient and often requires special operation modes where only a few buckets of the storage ring are filled. We designed a novel software defined photon counting system that allows to implement a variety of pump-probe schemes at the full repetition rate. The high number of photon counters allows to detect the response of the sample at multiple time delays simultaneously, thus improving the efficiency of the experiment. The system has been successfully applied to time resolved scanning transmission x-ray microscopy. However, this technique is applicable more generally.

An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

DOE PAGES

Höppner, H.; Hage, A.; Tanikawa, T.; ...

2015-05-15

High repetition rate free-electron lasers (FEL), producing highly intense extreme ultraviolet and x-ray pulses, require new high power tunable femtosecond lasers for FEL seeding and FEL pump-probe experiments. A tunable, 112 W (burst mode) optical parametric chirped-pulse amplifier (OPCPA) is demonstrated with center frequencies ranging from 720–900 nm, pulse energies up to 1.12 mJ and a pulse duration of 30 fs at a repetition rate of 100 kHz. Since the power scalability of this OPCPA is limited by the OPCPA-pump amplifier, we also demonstrate a 6.7–13.7 kW (burst mode) thin-disk OPCPA-pump amplifier, increasing the possible OPCPA output power to manymore » hundreds of watts. Furthermore, third and fourth harmonic generation experiments are performed and the results are used to simulate a seeded FEL with high-gain harmonic generation.« less

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).

Highly precise stabilization of intracavity prism-based Er:fiber frequency comb using optical-microwave phase detector.

PubMed

Zhang, Shuangyou; Wu, Jiutao; Leng, Jianxiao; Lai, Shunnan; Zhao, Jianye

2014-11-15

In this Letter, we demonstrate a fully stabilized Er:fiber frequency comb by using a fiber-based, high-precision optical-microwave phase detector. To achieve high-precision and long-term phase locking of the repetition rate to a microwave reference, frequency control techniques (tuning pump power and cavity length) are combined together as its feedback. Since the pump power has been used for stabilization of the repetition rate, we introduce a pair of intracavity prisms as a regulator for carrier-envelope offset frequency, thereby phase locking one mode of the comb to the rubidium saturated absorption transition line. The stabilized comb performs the same high stability as the reference for the repetition rate and provides a residual frequency instability of 3.6×10(-13) for each comb mode. The demonstrated stabilization scheme could provide a high-precision comb for optical communication, direct frequency comb spectroscopy.

Characteristics of a velvet cathode under high repetition rate pulse operation

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

Xun Tao; Zhang Jiande; Yang Hanwu

2009-10-15

As commonly used material for cold cathodes, velvet works well in single shot and low repetition rate (rep-rate) high-power microwave (HPM) sources. In order to determine the feasibility of velvet cathodes under high rep-rate operation, a series of experiments are carried out on a high-power diode, driven by a {approx}300 kV, {approx}6 ns, {approx}100 {omega}, and 1-300 Hz rep-rate pulser, Torch 02. Characteristics of vacuum compatibility and cathode lifetime under different pulse rep-rate are focused on in this paper. Results of time-resolved pressure history, diode performance, shot-to-shot reproducibility, and velvet microstructure changes are presented. As the rep-rate increases, the equilibriummore » pressure grows hyperlinearly and the velvet lifetime decreases sharply. At 300 Hz, the pressure in the given diode exceeded 1 Pa, and the utility shots decreased to 2000 pulses for nonstop mode. While, until the velvet begins to degrade, the pulse-to-pulse instability of diode voltage and current is quite small, even under high rep-rate conditions. Possible reasons for the operation limits are discussed, and methods to improve the performance of a rep-rate velvet cathode are also suggested. These results may be of interest to the repetitive HPM systems with cold cathodes.« less

Single-pulse picking at kHz repetition rates using a Ge plasma switch at the free-electron laser FELBE.

PubMed

Schmidt, J; Winnerl, S; Seidel, W; Bauer, C; Gensch, M; Schneider, H; Helm, M

2015-06-01

We demonstrate a system for picking of mid-infrared and terahertz (THz) radiation pulses from the free-electron laser (FEL) FELBE operating at a repetition rate of 13 MHz. Single pulses are reflected by a dense electron-hole plasma in a Ge slab that is photoexcited by amplified near-infrared (NIR) laser systems operating at repetition rates of 1 kHz and 100 kHz, respectively. The peak intensity of picked pulses is up to 400 times larger than the peak intensity of residual pulses. The required NIR fluence for picking pulses at wavelengths in the range from 5 μm to 30 μm is discussed. In addition, we show that the reflectivity of the plasma decays on a time scale from 100 ps to 1 ns dependent on the wavelengths of the FEL and the NIR laser. The plasma switch enables experiments with the FEL that require high peak power but lower average power. Furthermore, the system is well suited to investigate processes with decay times in the μs to ms regime, i.e., much longer than the 77 ns long pulse repetition period of FELBE.

Single-pulse picking at kHz repetition rates using a Ge plasma switch at the free-electron laser FELBE

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

Schmidt, J., E-mail: j.schmidt@hzdr.de; Helm, M.; Technische Universität Dresden, 01062 Dresden

2015-06-15

We demonstrate a system for picking of mid-infrared and terahertz (THz) radiation pulses from the free-electron laser (FEL) FELBE operating at a repetition rate of 13 MHz. Single pulses are reflected by a dense electron-hole plasma in a Ge slab that is photoexcited by amplified near-infrared (NIR) laser systems operating at repetition rates of 1 kHz and 100 kHz, respectively. The peak intensity of picked pulses is up to 400 times larger than the peak intensity of residual pulses. The required NIR fluence for picking pulses at wavelengths in the range from 5 μm to 30 μm is discussed. Inmore » addition, we show that the reflectivity of the plasma decays on a time scale from 100 ps to 1 ns dependent on the wavelengths of the FEL and the NIR laser. The plasma switch enables experiments with the FEL that require high peak power but lower average power. Furthermore, the system is well suited to investigate processes with decay times in the μs to ms regime, i.e., much longer than the 77 ns long pulse repetition period of FELBE.« less

Potential interactions among linguistic, autonomic, and motor factors in speech.

PubMed

Kleinow, Jennifer; Smith, Anne

2006-05-01

Though anecdotal reports link certain speech disorders to increases in autonomic arousal, few studies have described the relationship between arousal and speech processes. Additionally, it is unclear how increases in arousal may interact with other cognitive-linguistic processes to affect speech motor control. In this experiment we examine potential interactions between autonomic arousal, linguistic processing, and speech motor coordination in adults and children. Autonomic responses (heart rate, finger pulse volume, tonic skin conductance, and phasic skin conductance) were recorded simultaneously with upper and lower lip movements during speech. The lip aperture variability (LA variability index) across multiple repetitions of sentences that varied in length and syntactic complexity was calculated under low- and high-arousal conditions. High arousal conditions were elicited by performance of the Stroop color word task. Children had significantly higher lip aperture variability index values across all speaking tasks, indicating more variable speech motor coordination. Increases in syntactic complexity and utterance length were associated with increases in speech motor coordination variability in both speaker groups. There was a significant effect of Stroop task, which produced increases in autonomic arousal and increased speech motor variability in both adults and children. These results provide novel evidence that high arousal levels can influence speech motor control in both adults and children. (c) 2006 Wiley Periodicals, Inc.

Closed cycle high-repetition-rate pulsed HF laser

NASA Astrophysics Data System (ADS)

Harris, Michael R.; Morris, A. V.; Gorton, Eric K.

1997-04-01

The design and performance of a closed cycle high repetition rate HF laser is described. A short pulse, glow discharge is formed in a 10 SF6:1 H2 gas mixture at a total pressure of approximately 110 torr within a 15 by 0.5 by 0.5 cm3 volume. Transverse, recirculated gas flow adequate to enable repetitive operation up to 3 kHz is imposed by a centrifugal fan. The fan also forces the gas through a scrubber cell to eliminate ground state HF from the gas stream. An automated gas make-up system replenishes spent gas removed by the scrubber. Typical mean laser output powers up to 3 W can be maintained for extended periods of operation.

Age Differences in the Effects of Experimenter-Instructed Versus Self-Generated Strategy Use

PubMed Central

Hertzog, Christopher; Price, Jodi; Dunlosky, John

2013-01-01

Background/Study Context Interactive imagery is superior to rote repetition as an encoding strategy for paired associate (PA) recall. Younger and older individuals often rate these strategies as equally effective before they gain experience using each strategy. The present study investigated how experimenter-supervised and participant-chosen strategy experience affected younger and older adults’ knowledge about the effectiveness of these two strategies. Methods Ninety-nine younger (M = 19.0 years, SD = 1.4) and 90 older adults (M = 70.4 years, SD = 5.2) participated in the experiment. In learning a first PA list participants were either instructed to use imagery or repetition to study specific items (supervised) or could choose their own strategies (unsupervised). All participants were unsupervised on a second PA list to evaluate whether strategy experience affected strategy knowledge, strategy use, and PA recall. Results Both instruction groups learned about the superiority of imagery use through task experience, downgrading repetition ratings and upgrading imagery ratings on the second list. However, older adults showed less knowledge updating than did younger adults. Previously supervised younger adults increased their imagery use, improving PA recall; older adults maintained a higher level of repetition use. Conclusions Older adults update knowledge of the differential effectiveness of the rote and imagery strategies, but to a lesser degree than younger adults. Older adults manifest an inertial tendency to continue using the repetition strategy even though they have learned that it is inferior to interactive imagery. PMID:22224949

A Flexible Master Oscillator for a Thomson Scattering Pulse-Burst Laser System

NASA Astrophysics Data System (ADS)

den Hartog, D. J.; Young, W. C.

2015-11-01

A new master oscillator will be installed in the pulse-burst laser system used for high-rep-rate Thomson scattering on the MST experiment. This new master oscillator will enable pulse repetition rates up to 1 MHz, with the ability to program a burst of pulses with arbitrary and varying time separation between each pulse. In addition, the energy of each master oscillator pulse can be adjusted to compensate for gain variations in the power amplifier section of the laser system. This flexibility is accomplished by chopping a CW laser source with a high-bandwidth acousto-optic modulator (AOM). The laser source is a 1064 nm diode-pumped solid-state laser with continuous output power variable from 100 to 500 mW. The 2 mm diameter polarized beam is focused into the gallium phosphide crystal of the AOM, which deflects the beam by approximately 60 mrad. Beam deflection is controlled by a simple digital input pulse, and is capable of producing laser pulses of less than 20 ns width at repetition rates much greater than 1 MHz. These pulses from the output of the AOM will be collimated and propagated into the laser amplifier system, where they will be amplified to ~ 2 J/pulse and injected into the MST plasma. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences under Award Number DE-FC02-05ER54814, and by the National Science Foundation under Award Number PHY-0821899.

A Quantitative Analysis of Pulsed Signals Emitted by Wild Bottlenose Dolphins.

PubMed

Luís, Ana Rita; Couchinho, Miguel N; Dos Santos, Manuel E

2016-01-01

Common bottlenose dolphins (Tursiops truncatus), produce a wide variety of vocal emissions for communication and echolocation, of which the pulsed repertoire has been the most difficult to categorize. Packets of high repetition, broadband pulses are still largely reported under a general designation of burst-pulses, and traditional attempts to classify these emissions rely mainly in their aural characteristics and in graphical aspects of spectrograms. Here, we present a quantitative analysis of pulsed signals emitted by wild bottlenose dolphins, in the Sado estuary, Portugal (2011-2014), and test the reliability of a traditional classification approach. Acoustic parameters (minimum frequency, maximum frequency, peak frequency, duration, repetition rate and inter-click-interval) were extracted from 930 pulsed signals, previously categorized using a traditional approach. Discriminant function analysis revealed a high reliability of the traditional classification approach (93.5% of pulsed signals were consistently assigned to their aurally based categories). According to the discriminant function analysis (Wilk's Λ = 0.11, F3, 2.41 = 282.75, P < 0.001), repetition rate is the feature that best enables the discrimination of different pulsed signals (structure coefficient = 0.98). Classification using hierarchical cluster analysis led to a similar categorization pattern: two main signal types with distinct magnitudes of repetition rate were clustered into five groups. The pulsed signals, here described, present significant differences in their time-frequency features, especially repetition rate (P < 0.001), inter-click-interval (P < 0.001) and duration (P < 0.001). We document the occurrence of a distinct signal type-short burst-pulses, and highlight the existence of a diverse repertoire of pulsed vocalizations emitted in graded sequences. The use of quantitative analysis of pulsed signals is essential to improve classifications and to better assess the contexts of emission, geographic variation and the functional significance of pulsed signals.

Performance scaling via passive pulse shaping in cavity-enhanced optical parametric chirped-pulse amplification.

PubMed

Siddiqui, Aleem M; Moses, Jeffrey; Hong, Kyung-Han; Lai, Chien-Jen; Kärtner, Franz X

2010-06-15

We show that an enhancement cavity seeded at the full repetition rate of the pump laser can automatically reshape small-signal gain across the interacting pulses in an optical parametric chirped-pulse amplifier for close-to-optimal operation, significantly increasing both the gain bandwidth and the conversion efficiency, in addition to boosting gain for high-repetition-rate amplification. Applied to a degenerate amplifier, the technique can provide an octave-spanning gain bandwidth.

Production and Characterization of High Repetition Rate Terahertz Radiation in Femtosecond-Laser-Induced Air Plasma

DTIC Science & Technology

2009-03-01

nanometer, 50 femtosecond, 0.35 Watt, 40 KHz, pulsed Ti:Sapphire laser system was used as the source infrared beam. This beam was focused onto a...development of high speed THz imaging and spectroscopy systems. Until recently, the production and detection of coherent THz radiation has been both...exist a tabletop model that generates enough power at a high enough repetition rate to be feasible for most imaging or spectroscopy systems. The

High-speed carrier-envelope phase drift detection of amplified laser pulses.

PubMed

Fordell, T; Miranda, M; Arnold, C L; L'Huillier, A

2011-11-21

An instrument for measuring carrier-envelope phase (CEP) drift of amplified femtosecond laser pulses at repetition rates up to the 100-kHz regime is presented. The device can be used for real-time pulse labeling and it could also enable single-loop CEP control of future high-repetition rate laser amplifiers. The scheme is demonstrated by measuring the CEP drift of a 1-kHz source. © 2011 Optical Society of America

Bilateral coordination and the motor basis of female preference for sexual signals in canary song

PubMed Central

Suthers, Roderick A.; Vallet, Eric; Kreutzer, Michel

2012-01-01

SUMMARY The preference of female songbirds for particular traits in the songs of courting males has received considerable attention, but the relationship of preferred traits to male quality is poorly understood. Female domestic canaries (Serinus canaria, Linnaeus) preferentially solicit copulation with males that sing special high repetition rate, wide-band, multi-note syllables, called ‘sexy’ or A-syllables. Syllables are separated by minibreaths but each note is produced by pulsatile expiration, allowing high repetition rates and long duration phrases. The wide bandwidth is achieved by including two notes produced sequentially on opposite sides of the syrinx, in which the left and right sides are specialized for low or high frequencies, respectively. The emphasis of low frequencies is facilitated by a positive relationship between syllable repetition rate and the bandwidth of the fundamental frequency of notes sung by the left syrinx, such that bandwidth increases with increasing syllable repetition rate. The temporal offset between notes prevents cheating by unilaterally singing a note on the left side with a low fundamental frequency and prominent higher harmonics. The syringeal and respiratory motor patterns by which sexy syllables are produced support the hypothesis that these syllables provide a sensitive vocal–auditory indicator of a male's performance limit for the rapid, precisely coordinated interhemispheric switching, which is essential for many sensory and motor processes involving specialized contributions from each cerebral hemisphere. PMID:22875764

Neural coding of repetitive clicks in the medial geniculate body of cat.

PubMed

Rouiller, E; de Ribaupierre, Y; Toros-Morel, A; de Ribaupierre, F

1981-09-01

The activity of 418 medial geniculate body (MGB) units was studied in response to repetitive acoustic pulses in 35 nitrous oxide anaesthetized cats. The proportion of MGB neurons insensitive to repetitive clicks was close to 30%. On the basis of their pattern of discharge, the responsive units were divided into three categories. The majority of them (71%), classified as "lockers', showed discharges precisely time-locked to the individual clicks of the train. A few units (8%), called "groupers', had discharges loosely synchronized to low-rate repetitive clicks. When the spikes were not synchronized, the cell had transient or sustained responses for a limited frequency range and was classified as a "special responder' (21%). Responses of "lockers' were time-locked up to a limiting rate, which varied between 10 and 800 Hz; half of the "lockers' had a limiting rate of locking equal to or higher than 100 Hz. The degree of entrainment, defined as the probability that each click evokes at least one spike, regularly decreases for increasing rates; on the other hand, the precision of locking increasing increases with frequency. The time jitter observed at 100 Hz might be as small as 0.2 ms and was 1.2 ms on average. The population of "lockers' can mark with precision the transients of complex sounds and has response properties still compatible with a temporal coding of the fundamental frequency of most animal vocalizations.

In situ monitoring of laser-induced periodic surface structures formation on polymer films by grazing incidence small-angle X-ray scattering.

PubMed

Rebollar, Esther; Rueda, Daniel R; Martín-Fabiani, Ignacio; Rodríguez-Rodríguez, Álvaro; García-Gutiérrez, Mari-Cruz; Portale, Giuseppe; Castillejo, Marta; Ezquerra, Tiberio A

2015-04-07

The formation of laser-induced periodic surface structures (LIPSS) on model spin-coated polymer films has been followed in situ by grazing incidence small-angle X-ray scattering (GISAXS) using synchrotron radiation. The samples were irradiated at different repetition rates ranging from 1 up to 10 Hz by using the fourth harmonic of a Nd:YAG laser (266 nm) with pulses of 8 ns. Simultaneously, GISAXS patterns were acquired during laser irradiation. The variation of both the GISAXS signal with the number of pulses and the LIPSS period with laser irradiation time is revealing key kinetic aspects of the nanostructure formation process. By considering LIPSS as one-dimensional paracrystalline lattice and using a correlation found between the paracrystalline disorder parameter, g, and the number of reflections observed in the GISAXS patterns, the variation of the structural order of LIPSS can be assessed. The role of the laser repetition rate in the nanostructure formation has been clarified. For high pulse repetition rates (i.e., 10 Hz), LIPSS evolve in time to reach the expected period matching the wavelength of the irradiating laser. For lower pulse repetition rates LIPSS formation is less effective, and the period of the ripples never reaches the wavelength value. Results support and provide information on the existence of a feedback mechanism for LIPSS formation in polymer films.

Influence of the laser pulse repetition rate and scanning speed on the morphology of Ag nanostructures fabricated by pulsed laser ablation of solid target in water

NASA Astrophysics Data System (ADS)

Nikolov, A. S.; Balchev, I. I.; Nedyalkov, N. N.; Kostadinov, I. K.; Karashanova, D. B.; Atanasova, G. B.

2017-11-01

Nanostructures of noble metal were produced by pulsed laser ablation in liquid. A solid Ag target was immersed in double distilled water and a CuBr laser in a master oscillator—power amplifier configuration oscillating at 511 nm and emitting pulses with duration of 30 ns at a repetition rate of up to 20 kHz was employed to produce different colloids. The impact was studied of the laser pulse repetition rate and the beam scanning speed on the morphology of the nanostructures formed. Further, the optical extinction spectra of the colloids in the UV/VIS range were measured and used to make an indirect assessment of the changes in the shape and size distribution of the nanostructures. The transmission values in the near UV range were used to estimate the efficiency of the ablation process under the different experimental conditions implemented. A visualization of the nanostructures was made possible by transmission electron microscopy (TEM). The structure and phase composition of the nanoparticles were studied by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED), while the alteration of the target surface caused by the impact of the high-repetition-rate laser illumination was investigated by X-ray photoelectron spectroscopy (XPS). The optimal conditions were determined yielding the highest efficiency in terms of amount of ablated material.

Self-starting picosecond optical pulse source using stimulated Brillouin scattering in an optical fiber.

PubMed

Tang, W W; Shu, C

2005-02-21

We demonstrate a regeneratively mode-locked optical pulse source at about 10 GHz using an optoelectronic oscillator constructed with an electro-absorption modulator integrated distributed feedback laser diode. The 10 GHz RF component is derived from the interaction between the pump wave and the backscattered, frequency-downshifted Stokes wave resulted from stimulated Brillouin scattering in an optical fiber. The component serves as a modulation source for the 1556 nm laser diode without the need for any electrical or optical RF filter to perform the frequency extraction. Dispersion-compensated fiber, dispersion-shifted fiber, and standard single-mode fiber have been used respectively to generate optical pulses at variable repetition rates.

Repetitive Transcranial Magnetic Stimulation to Supplementary Motor Area in Refractory Obsessive-Compulsive Disorder Treatment: a Sham-Controlled Trial.

PubMed

Pelissolo, Antoine; Harika-Germaneau, Ghina; Rachid, Fady; Gaudeau-Bosma, Christian; Tanguy, Marie-Laure; BenAdhira, Rene; Bouaziz, Noomane; Popa, Traian; Wassouf, Issa; Saba, Ghassen; Januel, Dominique; Jaafari, Nematollah

2016-08-01

Repetitive transcranial magnetic stimulation has been explored in patients with obsessive-compulsive disorder, but with negative or conflicting results. This randomized double-blind study was designed to assess the efficacy of 1-Hz repetitive transcranial magnetic stimulation over the presupplementary area. Forty medication-resistant patients were assigned to 4 weeks of either active or sham repetitive transcranial magnetic stimulation targeting the presupplementary area with the help of a neuronavigation system. According to the Yale-Brown obsessive-compulsive scale, the baseline-week 4 evolution showed no significant differences between groups. Responder rates at week 4 were not different between groups (repetitive transcranial magnetic stimulation 10.5% vs sham 20%; P=.63). Low-frequency repetitive transcranial magnetic stimulation applied to the presupplementary area seems ineffective for the treatment of obsessive-compulsive disorder patients, at least in severe and drug-refractory cases such as those included in this study. Further research is required to determine profiles of responder patients and appropriate repetitive transcranial magnetic stimulation parameters for obsessive-compulsive disorder. © The Author 2016. Published by Oxford University Press on behalf of CINP.

A multi-train electrical stimulation protocol facilitates transcranial electrical motor evoked potentials and increases induction rate and reproducibility even in patients with preoperative neurological deficits.

PubMed

Ushio, Shuta; Kawabata, Shigenori; Sumiya, Satoshi; Kato, Tsuyoshi; Yoshii, Toshitaka; Yamada, Tsuyoshi; Enomoto, Mitsuhiro; Okawa, Atsushi

2018-06-01

This study sought to evaluate the facilitation effect of repetitive multi-train transcranial electrical stimulation (mt-TES) at 2 repetition rates on transcranial electrical motor evoked potential (Tc-MEP) monitoring during spinal surgery, and to assess the induction rate in patients with impaired motor function from a compromised spinal cord or spinal nerve. We studied 32 consecutive patients with impaired motor function undergoing cervical or thoracic spinal surgery (470 muscles). A series of 10 TESs with 5 pulse trains were preoperatively delivered at 2 repetition rates (1 and 5 Hz). All peak-topeak amplitudes of the MEPs of the upper and lower extremity muscles elicited by the 10 TESs were measured. The induction rates of the lower extremity muscles were also assessed with muscle and preoperative lower extremity motor function scores. In each of the muscles, MEP amplitudes were augmented by about 2-3 times at 1 Hz and 5-6 times at 5 Hz. Under the 5-Hz condition, all limb muscles showed significant amplification. Also, in all preoperative motor function score groups, the amplitudes and induction rates of the lower extremity muscles were significantly increased. Moreover, the facilitation effects tended to peak in the last half of the series of 10 TESs. In all score groups of patients with preoperative neurological deficits, repetitive mt-TES delivered at a frequency of 5 Hz markedly facilitated the MEPs of all limb muscles and increased the induction rate. We recommend this method to improve the reliability of intraoperative monitoring during spinal surgery.

Photocathodes for High Repetition Rate Light Sources

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

Ben-Zvi, Ilan

2014-04-20

This proposal brought together teams at Brookhaven National Laboratory (BNL), Lawrence Berkeley National Laboratory (LBNL) and Stony Brook University (SBU) to study photocathodes for high repetition rate light sources such as Free Electron Lasers (FEL) and Energy Recovery Linacs (ERL). Below details the Principal Investigators and contact information. Each PI submits separately for a budget through his corresponding institute. The work done under this grant comprises a comprehensive program on critical aspects of the production of the electron beams needed for future user facilities. Our program pioneered in situ and in operando diagnostics for alkali antimonide growth. The focus ismore » on development of photocathodes for high repetition rate Free Electron Lasers (FELs) and Energy Recovery Linacs (ERLs), including testing SRF photoguns, both normal-­conducting and superconducting. Teams from BNL, LBNL and Stony Brook University (SBU) led this research, and coordinated their work over a range of topics. The work leveraged a robust infrastructure of existing facilities and the support was used for carrying out the research at these facilities. The program concentrated in three areas: a) Physics and chemistry of alkali-­antimonide cathodes (BNL – LBNL) b) Development and testing of a diamond amplifier for photocathodes (SBU -­ BNL) c) Tests of both cathodes in superconducting RF photoguns (SBU) and copper RF photoguns (LBNL) Our work made extensive use of synchrotron radiation materials science techniques, such as powder-­ and single-­crystal diffraction, x-­ray fluorescence, EXAFS and variable energy XPS. BNL and LBNL have many complementary facilities at the two light sources associated with these laboratories (NSLS and ALS, respectively); use of these will be a major thrust of our program and bring our understanding of these complex materials to a new level. In addition, CHESS at Cornell will be used to continue seamlessly throughout the NSLS dark period and new diffraction facilities at ALS will be utilized. We also will continue to make use of the excellent analytical facilities at the CNF (BNL) and the Molecular Foundry (LBNL), where we have access to state of the art UHV XPS, SPM, SEM and scanning Auger microscopy.« less

Development of speech motor control: lip movement variability.

PubMed

Schötz, Susanne; Frid, Johan; Löfqvist, Anders

2013-06-01

This study examined variability of lip movements across repetitions of the same utterance as a function of age in Swedish speakers. The specific purpose was to extend earlier findings by examining variability in both phase and amplitude. Subjects were 50 typically developed native Swedish children and adults (28 females, 22 males, aged 5 to 31 yr). Lip movements were recorded during 15 to 20 repetitions of a short Swedish phrase using three-dimensional articulography. After correction for head movements, the kinematic records were expressed in a maxilla-based coordinate system. Movement onset and offset of the utterance were identified using kinematic landmarks. The Euclidean distance between receivers on the upper and lower lips was calculated and subjected to functional data analysis to assess both phase and amplitude variability. Results show a decrease in both indices as a function of age, with a greater reduction of amplitude variability. There was no difference between males and females for either index. The two indices were moderately correlated with each other, suggesting that they capture different aspects of speech production. Utterance duration also decreased with age, but variability was unrelated to duration. The standard deviation of utterance duration also decreased with age. The present results thus suggest that age related changes in speech motor control continue up until 30 years of age.

Gentle vs. aversive handling of pregnant ewes: II. Physiology and behavior of the lambs.

PubMed

Coulon, M; Hild, S; Schroeer, A; Janczak, A M; Zanella, A J

2011-07-06

We compared the effects of aversive and gentle handling in late pregnant ewes on fearfulness, heart rate variability and spatial learning in lambs. Twenty-four Norwegian-Dala ewes were studied. Ewes were subjected to gentle (i.e. soft talking and calm behavior) or aversive handling (i.e. swift movements and shouting) for 10 min twice a day during the last five weeks of pregnancy. Lambs from aversively (AVS) or gently (GEN) treated ewes were tested at 4 weeks of age. Lamb behavior was recorded during a) a human approach test, composed of 4 min of isolation and 4 min of exposure to an unfamiliar human, b) an umbrella startle test followed by 5-min recording, and c) two repetitions of a maze test. In addition, heart rate variability was recorded telemetrically before and after the human and startle tests. The baseline heart rate variability measures suggested a lower influence of vagal stimulation in AVS lambs. In the human approach test, AVS lambs vocalized and explored the environment less, and were slower to approach the human. They also tended to have higher flight distances during the startle test than the GEN lambs. The prenatal treatment had no significant effect in the maze test. In conclusion, we showed that aversive handling of pregnant ewes increased fearfulness and reduced vagal tone in their progeny compared to GEN lambs. These effects can have consequences for how lambs cope with rearing conditions. Copyright © 2011 Elsevier Inc. All rights reserved.

Prediction of the Maximum Number of Repetitions and Repetitions in Reserve From Barbell Velocity.

PubMed

García-Ramos, Amador; Torrejón, Alejandro; Feriche, Belén; Morales-Artacho, Antonio J; Pérez-Castilla, Alejandro; Padial, Paulino; Haff, Guy Gregory

2018-03-01

To provide 2 general equations to estimate the maximum possible number of repetitions (XRM) from the mean velocity (MV) of the barbell and the MV associated with a given number of repetitions in reserve, as well as to determine the between-sessions reliability of the MV associated with each XRM. After determination of the bench-press 1-repetition maximum (1RM; 1.15 ± 0.21 kg/kg body mass), 21 men (age 23.0 ± 2.7 y, body mass 72.7 ± 8.3 kg, body height 1.77 ± 0.07 m) completed 4 sets of as many repetitions as possible against relative loads of 60%1RM, 70%1RM, 80%1RM, and 90%1RM over 2 separate sessions. The different loads were tested in a randomized order with 10 min of rest between them. All repetitions were performed at the maximum intended velocity. Both the general equation to predict the XRM from the fastest MV of the set (CV = 15.8-18.5%) and the general equation to predict MV associated with a given number of repetitions in reserve (CV = 14.6-28.8%) failed to provide data with acceptable between-subjects variability. However, a strong relationship (median r 2  = .984) and acceptable reliability (CV < 10% and ICC > .85) were observed between the fastest MV of the set and the XRM when considering individual data. These results indicate that generalized group equations are not acceptable methods for estimating the XRM-MV relationship or the number of repetitions in reserve. When attempting to estimate the XRM-MV relationship, one must use individualized relationships to objectively estimate the exact number of repetitions that can be performed in a training set.

Interactive effects of age-of-acquisition and repetition priming in the lexical decision task. A multiple-loci account.

PubMed

Spataro, Pietro; Longobardi, Emiddia; Saraulli, Daniele; Rossi-Arnaud, Clelia

2013-01-01

The analysis of the interaction between repetition priming and age of acquisition may be used to shed further light on the question of which stages of elaboration are affected by this psycholinguistic variable. In the present study we applied this method in the context of two versions of a lexical decision task that differed in the type of non-words employed at test. When the non-words were illegal and unpronounceable, repetition priming was primarily based on the analysis of orthographic information, while phonological processes were additionally recruited only when using legal pronounceable non-words. The results showed a significant interaction between repetition priming and age of acquisition in both conditions, with priming being greater for late- than for early-acquired words. These findings support a multiple-loci account, indicating that age of acquisition influences implicit memory by facilitating the retrieval of both the orthographic and the phonological representations of studied words.

Child Maltreatment and Repeat Presentations to the Emergency Department for Suicide-Related Behaviors

ERIC Educational Resources Information Center

Rhodes, Anne E.; Boyle, Michael H.; Bethell, Jennifer; Wekerle, Christine; Tonmyr, Lil; Goodman, Deborah; Leslie, Bruce; Lam, Kelvin; Manion, Ian

2013-01-01

Objectives: To identify factors associated with repeat emergency department (ED) presentations for suicide-related behaviors (SRB)--hereafter referred to as repetition--among children/youth to aid secondary prevention initiatives. To compare rates of repetition in children/youth with substantiated maltreatment requiring removal from their parental…

Serial Recall and Nonword Repetition in Reading Disabled Children.

ERIC Educational Resources Information Center

Roodenrys, Steven; Stokes, Julie

2001-01-01

Examines the performance on verbal short-term memory tasks of specifically reading disabled children relative to reading-age matched and chronological-age matched control groups. Examines memory span for words, highly wordlike nonwords and less wordlike nonwords, speech rates for these items, and nonword repetition. Suggests that there is a…

Influence of pulse repetition rate on temperature rise and working time during composite filling removal with the Er:YAG laser.

PubMed

Correa-Afonso, Alessandra M; Pécora, Jesus Djalma; Palma-Dibb, Regina G

2008-06-01

The purpose of this study was to assess the efficacy of Er:YAG laser energy for composite resin removal and the influence of pulse repetition rate on the thermal alterations occurring during laser ablation. Composite resin filling was placed in cavities (1.0 mm deep) prepared in bovine teeth and the specimens were randomly assigned to five groups according to the technique used for composite filling removal. In group I (controls), the restorations were removed using a high-speed diamond bur. In the other groups, the composite fillings were removed using an Er:YAG laser with different pulse repetition rates: group 2-2 Hz; group 3-4 Hz; group 4-6 Hz; and group 5-10 Hz. The time required for complete removal of the restorative material and the temperature changes were recorded. Temperature rise during composite resin removal with the Er:YAG laser occurred in the substrate underneath the restoration and was directly proportional to the increase in pulse repetition rate. None of the groups had a temperature increase during composite filling removal of more than 5.6 degrees C, which is considered the critical point above which irreversible thermal damage to the pulp may result. Regarding the time for composite filling removal, all the laser-ablated groups (except for group 5 [10 Hz]) required more time than the control group for complete elimination of the material from the cavity walls. Under the tested conditions, Er:YAG laser irradiation was efficient for composite resin ablation and did not cause a temperature increase above the limit considered safe for the pulp. Among the tested pulse repetition rates, 6 Hz produced minimal temperature change compared to the control group (high-speed bur), and allowed composite filling removal within a time period that is acceptable for clinical conditions.

The annotation of repetitive elements in the genome of channel catfish (Ictalurus punctatus).

PubMed

Yuan, Zihao; Zhou, Tao; Bao, Lisui; Liu, Shikai; Shi, Huitong; Yang, Yujia; Gao, Dongya; Dunham, Rex; Waldbieser, Geoff; Liu, Zhanjiang

2018-01-01

Channel catfish (Ictalurus punctatus) is a highly adaptive species and has been used as a research model for comparative immunology, physiology, and toxicology among ectothermic vertebrates. It is also economically important for aquaculture. As such, its reference genome was generated and annotated with protein coding genes. However, the repetitive elements in the catfish genome are less well understood. In this study, over 417.8 Megabase (MB) of repetitive elements were identified and characterized in the channel catfish genome. Among them, the DNA/TcMar-Tc1 transposons are the most abundant type, making up ~20% of the total repetitive elements, followed by the microsatellites (14%). The prevalence of repetitive elements, especially the mobile elements, may have provided a driving force for the evolution of the catfish genome. A number of catfish-specific repetitive elements were identified including the previously reported Xba elements whose divergence rate was relatively low, slower than that in untranslated regions of genes but faster than the protein coding sequences, suggesting its evolutionary restrictions.

The annotation of repetitive elements in the genome of channel catfish (Ictalurus punctatus)

PubMed Central

Yuan, Zihao; Zhou, Tao; Bao, Lisui; Liu, Shikai; Shi, Huitong; Yang, Yujia; Gao, Dongya; Dunham, Rex; Waldbieser, Geoff

2018-01-01

Channel catfish (Ictalurus punctatus) is a highly adaptive species and has been used as a research model for comparative immunology, physiology, and toxicology among ectothermic vertebrates. It is also economically important for aquaculture. As such, its reference genome was generated and annotated with protein coding genes. However, the repetitive elements in the catfish genome are less well understood. In this study, over 417.8 Megabase (MB) of repetitive elements were identified and characterized in the channel catfish genome. Among them, the DNA/TcMar-Tc1 transposons are the most abundant type, making up ~20% of the total repetitive elements, followed by the microsatellites (14%). The prevalence of repetitive elements, especially the mobile elements, may have provided a driving force for the evolution of the catfish genome. A number of catfish-specific repetitive elements were identified including the previously reported Xba elements whose divergence rate was relatively low, slower than that in untranslated regions of genes but faster than the protein coding sequences, suggesting its evolutionary restrictions. PMID:29763462

Deep Investigation of Arabidopsis thaliana Junk DNA Reveals a Continuum between Repetitive Elements and Genomic Dark Matter

PubMed Central

Maumus, Florian; Quesneville, Hadi

2014-01-01

Eukaryotic genomes contain highly variable amounts of DNA with no apparent function. This so-called junk DNA is composed of two components: repeated and repeat-derived sequences (together referred to as the repeatome), and non-annotated sequences also known as genomic dark matter. Because of their high duplication rates as compared to other genomic features, transposable elements are predominant contributors to the repeatome and the products of their decay is thought to be a major source of genomic dark matter. Determining the origin and composition of junk DNA is thus important to help understanding genome evolution as well as host biology. In this study, we have used a combination of tools enabling to show that the repeatome from the small and reducing A. thaliana genome is significantly larger than previously thought. Furthermore, we present the concepts and results from a series of innovative approaches suggesting that a significant amount of the A. thaliana dark matter is of repetitive origin. As a tentative standard for the community, we propose a deep compendium annotation of the A. thaliana repeatome that may help addressing farther genome evolution as well as transcriptional and epigenetic regulation in this model plant. PMID:24709859

Single-exposure visual memory judgments are reflected in inferotemporal cortex

PubMed Central

Meyer, Travis

2018-01-01

Our visual memory percepts of whether we have encountered specific objects or scenes before are hypothesized to manifest as decrements in neural responses in inferotemporal cortex (IT) with stimulus repetition. To evaluate this proposal, we recorded IT neural responses as two monkeys performed a single-exposure visual memory task designed to measure the rates of forgetting with time. We found that a weighted linear read-out of IT was a better predictor of the monkeys’ forgetting rates and reaction time patterns than a strict instantiation of the repetition suppression hypothesis, expressed as a total spike count scheme. Behavioral predictions could be attributed to visual memory signals that were reflected as repetition suppression and were intermingled with visual selectivity, but only when combined across the most sensitive neurons. PMID:29517485

Damping of acoustic waves in a 1 kHz repetition rate XeCl laser

NASA Astrophysics Data System (ADS)

Sentis, M. L.; Canarelli, P.; Delaporte, Ph.; Forestier, B. M.; Fontaine, B. L.

To increase the pulse repetition frequency, the average power, and the beam quality of excimer laser systems, the problem of damping of the strong acoustic waves induced by the active medium excitation must be solved. In order to achieve this goal, different electrodes and acoustic damping configuration have been studied. Excitation of the active medium at high repetition rate (up to 1000 Hz) in a subsonic loop was achieved by means of a classical discharge, through transfer capacitors. The discharge is preionized by X-rays generated by a wire ion plasma gun. The effects of different kinds of electrodes (solid, screen, nickel felt) and transversal acoustic dampers on the stability of the discharge and on the pulse to pulse output energy are discussed.

A Device and Methodology for Measuring Repetitive Lifting VO2max (Oxygen Consumption Rate)

DTIC Science & Technology

1987-08-01

variety of lifting and lowering tasks There have been no dcvice related injuries and little down time due to mechanical failure du ng more than 560 1hours...uptake procedure and is suitable to be used for a wide variety of lifting and lowering tasks. There have been no device related injuries and little...worker productivity and decreased injury rates. What has not been -examined in industrial research is high intensity, maximal effort repetitive lifting

Dual-color three-dimensional STED microscopy with a single high-repetition-rate laser

PubMed Central

Han, Kyu Young; Ha, Taekjip

2016-01-01

We describe a dual-color three-dimensional stimulated emission depletion (3D-STED) microscopy employing a single laser source with a repetition rate of 80 MHz. Multiple excitation pulses synchronized with a STED pulse were generated by a photonic crystal fiber and the desired wavelengths were selected by an acousto-optic tunable filter with high spectral purity. Selective excitation at different wavelengths permits simultaneous imaging of two fluorescent markers at a nanoscale resolution in three dimensions. PMID:26030581

Microwave-triggered laser switch

DOEpatents

Piltch, M.S.

1982-05-19

A high-repetition rate switch is described for delivering short duration, high-powered electrical pulses from a pulsed-charged dc power supply. The present invention utilizes a microwave-generating device such as a magnetron that is capable of producing high-power pulses at high-pulse repetition rates and fast-pulse risetimes for long periods with high reliability. The rail-gap electrodes provide a large surface area that reduces induction effects and minimizes electrode erosion. Additionally, breakdown is initiated in a continuous geometric fashion that also increases operating lifetime of the device.

Microwave-triggered laser switch

DOEpatents

Piltch, Martin S.

1984-01-01

A high-repetition rate switch for delivering short duration, high-power electrical pulses from a pulsed-charged dc power supply. The present invention utilizes a microwave-generating device such as a magnetron that is capable of producing high-power pulses at high-pulse repetition rates and fast-pulse risetimes for long periods with high reliability. The rail-gap electrodes provide a large surface area that reduces induction effects and minimizes electrode erosion. Additionally, breakdown is initiated in a continuous geometric fashion that also increases operating lifetime of the device.

HiLASE Project: high intensity lasers for industrial and scientific applications

NASA Astrophysics Data System (ADS)

Rostohar, Danijela; Lucianetti, Antonio; Endo, Akira; Mocek, Tomas

2015-01-01

The Czech national R&D project HiLASE is a platform for development of advance high repetition rate, diode pump solid state lasers (DPSSL) systems with energies in the range from mJ to 10J and repetition rate from 10 Hz to 100 kHz. In this paper an overview and a status of the project will be given. Additionally some applications of these lasers in the hi-tech industry, which initiated their development, will be also presented.

High-precision cutting of polyimide film using femtosecond laser for the application in flexible electronics

NASA Astrophysics Data System (ADS)

Ganin, D. V.; Lapshin, K. E.; Obidin, A. Z.; Vartapetov, S. K.

2018-01-01

The experimental results of cutting a polyimide film on the optical glass substrate by means of femtosecond lasers are given. Two modes of laser cutting of this film without damages to a glass base are determined. The first is the photo graphitization using a high repetition rate femtosecond laser. The second is ablative, under the effect of femtosecond laser pulses with high energy and low repetition rate. Cutting of semiconductor chips formed on the polyimide film surface is successfully demonstrated.

High repetition rate ultrashort laser cuts a path through fog

NASA Astrophysics Data System (ADS)

de la Cruz, Lorena; Schubert, Elise; Mongin, Denis; Klingebiel, Sandro; Schultze, Marcel; Metzger, Thomas; Michel, Knut; Kasparian, Jérôme; Wolf, Jean-Pierre

2016-12-01

We experimentally demonstrate that the transmission of a 1030 nm, 1.3 ps laser beam of 100 mJ energy through fog increases when its repetition rate increases to the kHz range. Due to the efficient energy deposition by the laser filaments in the air, a shockwave ejects the fog droplets from a substantial volume of the beam, at a moderate energy cost. This process opens prospects for applications requiring the transmission of laser beams through fogs and clouds.

Broadly tunable, low timing jitter, high repetition rate optoelectronic comb generator

PubMed Central

Metcalf, A. J.; Quinlan, F.; Fortier, T. M.; Diddams, S. A.; Weiner, A. M.

2016-01-01

We investigate the low timing jitter properties of a tunable single-pass optoelectronic frequency comb generator. The scheme is flexible in that both the repetition rate and center frequency can be continuously tuned. When operated with 10 GHz comb spacing, the integrated residual pulse-to-pulse timing jitter is 11.35 fs (1 Hz to 10 MHz) with no feedback stabilization. The corresponding phase noise at 1 Hz offset from the photodetected 10 GHz carrier is −100 dBc/Hz. PMID:26865734

Impact of dehydration on a full body resistance exercise protocol.

PubMed

Kraft, Justin A; Green, James M; Bishop, Phillip A; Richardson, Mark T; Neggers, Yasmin H; Leeper, James D

2010-05-01

This study examined effects of dehydration on a full body resistance exercise workout. Ten males completed two trials: heat exposed (with 100% fluid replacement) (HE) and dehydration (approximately 3% body mass loss with no fluid replacement) (DEHY) achieved via hot water bath (approximately 39 degrees C). Following HE and DEHY, participants performed three sets to failure (using predetermined 12 repetition maximum) of bench press, lat pull down, overhead press, barbell curl, triceps press, and leg press with a 2-min recovery between each set and 2 min between exercises. A paired t test showed total repetitions (all sets combined) were significantly lower for DEHY: (144.1 +/- 26.6 repetitions) versus HE: (169.4 +/- 29.1 repetitions). ANOVAs showed significantly lower repetitions (approximately 1-2 repetitions on average) per exercise for DEHY versus HE (all exercises). Pre-set rate of perceived exertion (RPE) and pre-set heart rate (HR) were significantly higher [approximately 0.6-1.1 units on average in triceps press, leg press, and approached significance in lat pull down (P = 0.14) and approximately 6-13 b min(-1) on average in bench press, lat pull down, triceps press, and approached significance for overhead press (P = 0.10)] in DEHY versus HE. Session RPE difference approached significance (DEHY: 8.6 +/- 1.9, HE: 7.4 +/- 2.3) (P = 0.12). Recovery HR was significantly higher for DEHY (116 +/- 15 b min(-1)) versus HE (105 +/- 13 b min(-1)). Dehydration (approximately 3%) impaired resistance exercise performance, decreased repetitions, increased perceived exertion, and hindered HR recovery. Results highlight the importance of adequate hydration during full body resistance exercise sessions.

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

Boumaaraf, Abdelâali, E-mail: aboumaaraf@yahoo.fr; University of Farhat Abbas Setif1, Sétif, 19000; Mohamadi, Tayeb

In this paper, we present the FPGA implementation of the multiple pulse width modulation (MPWM) signal generation with repetition of data segments, applied to the variable frequency variable voltage systems and specially at to the photovoltaic water pumping system, in order to generate a signal command very easily between 10 Hz to 60 Hz with a small frequency and reduce the cost of the control system.

Intracavity KTP optical parametric oscillator driven by a KLM Nd:GGG laser with a single AO modulator

NASA Astrophysics Data System (ADS)

Chu, Hongwei; Zhao, Shengzhi; Yang, Kejian; Zhao, Jia; Li, Yufei; Li, Tao; Li, Guiqiu; Li, Dechun; Qiao, Wenchao

2015-05-01

An intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a Kerr lens mode-locking (KLM) Nd:GGG laser near 1062 nm with a single AO modulator was realized for the first time. The mode-locking pulses of the signal wave were obtained with a short duration of subnanosecond and a repetition rate of several kilohertz (kHz). Under a diode pump power of 8.25 W, a maximum output power of 104 mW at signal wavelength near 1569 nm was obtained at a repetition rate of 2 kHz. The highest pulse energy and peak power were estimated to be 80 μJ and 102 kW at a repetition rate of 1 kHz, respectively. The shortest pulse duration was measured to be 749 ps. By considering the Gaussian spatial distribution of the photon density and the Kerr-lens effect in the gain medium, a set of the coupled rate equations for QML intracavity optical parametric oscillator are given and the numerical simulations are basically fitted with the experimental results.

Effects of caffeine and aspirin on light resistance training performance, perceived exertion, and pain perception.

PubMed

Hudson, Geoffrey M; Green, J Matt; Bishop, Phillip A; Richardson, Mark T

2008-11-01

This study compared independent effects of caffeine and aspirin on muscular endurance (repetitions), heart rate (HR), perceived exertion (RPE), and perceived pain index (PPI) during light resistance training bouts performed to volitional failure. It was hypothesized that the hypoalgesic properties of these ergogenic aids would decrease pain perception and potentially result in enhanced performance. College-aged men (n = 15) participated in a within-subjects, double-blind study with three independent, counterbalanced sessions wherein aspirin (10 mg x kg(-1)), caffeine (6 mg x kg(-1)), or matched placebo were ingested 1 hour before exercise, and RPE, HR, PPI, and repetitions (per set and total per exercise) were recorded at 100% of individual, predetermined, 12-repetition maximum for leg extensions (LE) and seated arm curls (AC). Repeated-measures analyses of variance were used for between-trial comparisons. Caffeine resulted in significantly greater (p < 0.05) HR (LE and AC), total repetitions (LE), and repetitions in set 1 (LE and AC) compared with aspirin and placebo. Aspirin resulted in significantly higher PPI in set 1 (LE). In LE, 47% of participants' performance exceeded the predetermined effect size (>or= 5 repetitions) for total repetitions, with 53% exceeding the effect size (>or= 2 repetitions) for repetitions in set 1 with caffeine (vs. placebo). In AC, 53% (total repetitions) and 47% (set 1 repetitions) of participants exceeded effect sizes with caffeine (vs. placebo), with only 13% experiencing decrements in performance (total repetitions). Aspirin also produced a higher PPI and RPE overall and in set 1 (vs. placebo). This study demonstrates that caffeine significantly enhanced resistance training performance in LE and AC, whereas aspirin did not. Athletes may improve their resistance training performance by acute ingestion of caffeine. As with most ergogenic aids, our analyses indicate that individual responses vary greatly.

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

PubMed Central

McGaha, Jamie; Miller, Kim; Descatha, Alexis; Welch, Laurie; Buchholz, Bryan; Evanoff, Bradley; Dale, Ann Marie

2014-01-01

Introduction Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks. Methods We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds. Results Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces. Conclusions Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders. PMID:24274895

Ultrashort pulse high repetition rate laser system for biological tissue processing

DOEpatents

Neev, Joseph; Da Silva, Luiz B.; Matthews, Dennis L.; Glinsky, Michael E.; Stuart, Brent C.; Perry, Michael D.; Feit, Michael D.; Rubenchik, Alexander M.

1998-01-01

A method and apparatus is disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment.

[Infiltration characteristics of soil water on loess slope land under intermittent and repetitive rainfall conditions].

PubMed

Li, Yi; Shao, Ming-An

2008-07-01

Based on the experiments of controlled intermittent and repetitive rainfall on slope land, the infiltration and distribution characteristics of soil water on loess slope land were studied. The results showed that under the condition of intermittent rainfall, the cumulative runoff during two rainfall events increased linearly with time, and the wetting front also increased with time. In the interval of the two rainfall events, the wetting front increased slowly, and the infiltration rate was smaller on steeper slope than on flat surface. During the second rainfall event, there was an obvious decreasing trend of infiltration rate with time. The cumulative infiltration on 15 degrees slope land was larger than that of 25 degrees slope land, being 178 mm and 88 mm, respectively. Under the condition of repetitive rainfall, the initial infiltration rate during each rainfall event was relatively large, and during the first rainfall, both the infiltration rate and the cumulative infiltration at various stages were larger than those during the other three rainfall events. However, after the first rainfall, there were no obvious differences in the infiltration rate among the next three rainfall events. The more the rainfall event, the deeper the wetting front advanced.

Ultrashort pulse high repetition rate laser system for biological tissue processing

DOEpatents

Neev, J.; Da Silva, L.B.; Matthews, D.L.; Glinsky, M.E.; Stuart, B.C.; Perry, M.D.; Feit, M.D.; Rubenchik, A.M.

1998-02-24

A method and apparatus are disclosed for fast, efficient, precise and damage-free biological tissue removal using an ultrashort pulse duration laser system operating at high pulse repetition rates. The duration of each laser pulse is on the order of about 1 fs to less than 50 ps such that energy deposition is localized in a small depth and occurs before significant hydrodynamic motion and thermal conduction, leading to collateral damage, can take place. The depth of material removed per pulse is on the order of about 1 micrometer, and the minimal thermal and mechanical effects associated with this ablation method allows for high repetition rate operation, in the region 10 to over 1000 Hertz, which, in turn, achieves high material removal rates. The input laser energy per ablated volume of tissue is small, and the energy density required to ablate material decreases with decreasing pulse width. The ablation threshold and ablation rate are only weakly dependent on tissue type and condition, allowing for maximum flexibility of use in various biological tissue removal applications. The use of a chirped-pulse amplified Titanium-doped sapphire laser is disclosed as the source in one embodiment. 8 figs.

Ablation dynamics - from absorption to heat accumulation/ultra-fast laser matter interaction

NASA Astrophysics Data System (ADS)

Kramer, Thorsten; Remund, Stefan; Jäggi, Beat; Schmid, Marc; Neuenschwander, Beat

2018-05-01

Ultra-short laser radiation is used in manifold industrial applications today. Although state-of-the-art laser sources are providing an average power of 10-100 W with repetition rates of up to several megahertz, most applications do not benefit from it. On the one hand, the processing speed is limited to some hundred millimeters per second by the dynamics of mechanical axes or galvanometric scanners. On the other hand, high repetition rates require consideration of new physical effects such as heat accumulation and shielding that might reduce the process efficiency. For ablation processes, process efficiency can be expressed by the specific removal rate, ablated volume per time, and average power. The analysis of the specific removal rate for different laser parameters, like average power, repetition rate or pulse duration, and process parameters, like scanning speed or material, can be used to find the best operation point for microprocessing applications. Analytical models and molecular dynamics simulations based on the so-called two-temperature model reveal the causes for the appearance of limiting physical effects. The findings of models and simulations can be used to take advantage and optimize processing strategies.

The development of a repetition-load scheme for the eccentric-only bench press exercise.

PubMed

Moir, Gavin L; Erny, Kyle F; Davis, Shala E; Guers, John J; Witmer, Chad A

2013-01-01

The purpose of the present study was to develop a repetition-load scheme for the eccentric-only bench press exercise. Nine resistance trained men (age: 21.6 ± 1.0 years; 1-repetition maximum [RM] bench press: 137.7 ± 30.4 kg) attended four testing sessions during a four week period. During the first session each subject's 1-RM bench press load utilizing the stretch-shortening cycle was determined. During the remaining sessions they performed eccentric-only repetitions to failure using supra-maximal loads equivalent to 110%, 120% and 130% of their 1-RM value with a constant cadence (30 reps·min(-1)). Force plates and a three dimensional motion analysis system were used during these final three sessions in order to evaluate kinematic and kinetic variables. More repetitions were completed during the 110% 1-RM condition compared to the 130% 1-RM condition (p=0.01). Mean total work (p=0.046) as well as vertical force (p=0.049), vertical work (p=0.017), and vertical power output (p=0.05) were significantly greater during the 130% 1-RM condition compared to the 110% 1-RM condition. A linear function was fitted to the number of repetitions completed under each load condition that allowed the determination of the maximum number of repetitions that could be completed under other supra-maximal loads. This linear function predicted an eccentric-only 1-RM in the bench press with a load equivalent to 164.8% 1-RM, producing a load of 227.0 ± 50.0 kg. The repetition-load scheme presented here should provide a starting point for researchers to investigate the kinematic, kinetic and metabolic responses to eccentric-only bench press workouts.

The Development of a Repetition-Load Scheme for the Eccentric-Only Bench Press Exercise

PubMed Central

Moir, Gavin L.; Erny, Kyle F.; Davis, Shala E.; Guers, John J.; Witmer, Chad A.

2013-01-01

The purpose of the present study was to develop a repetition-load scheme for the eccentric-only bench press exercise. Nine resistance trained men (age: 21.6 ± 1.0 years; 1-repetition maximum [RM] bench press: 137.7 ± 30.4 kg) attended four testing sessions during a four week period. During the first session each subject’s 1-RM bench press load utilizing the stretch-shortening cycle was determined. During the remaining sessions they performed eccentric-only repetitions to failure using supra-maximal loads equivalent to 110%, 120% and 130% of their 1-RM value with a constant cadence (30 reps·min−1). Force plates and a three dimensional motion analysis system were used during these final three sessions in order to evaluate kinematic and kinetic variables. More repetitions were completed during the 110% 1-RM condition compared to the 130% 1-RM condition (p=0.01). Mean total work (p=0.046) as well as vertical force (p=0.049), vertical work (p=0.017), and vertical power output (p=0.05) were significantly greater during the 130% 1-RM condition compared to the 110% 1-RM condition. A linear function was fitted to the number of repetitions completed under each load condition that allowed the determination of the maximum number of repetitions that could be completed under other supra-maximal loads. This linear function predicted an eccentric-only 1-RM in the bench press with a load equivalent to 164.8% 1-RM, producing a load of 227.0 ± 50.0 kg. The repetition-load scheme presented here should provide a starting point for researchers to investigate the kinematic, kinetic and metabolic responses to eccentric-only bench press workouts. PMID:24235981

Print exposure modulates the effects of repetition priming during sentence reading.

PubMed

Lowder, Matthew W; Gordon, Peter C

2017-12-01

Individual readers vary greatly in the quality of their lexical representations, and consequently in how quickly and efficiently they can access orthographic and lexical knowledge. This variability may be explained, at least in part, by individual differences in exposure to printed language, because practice at reading promotes the development of stronger reading skills. In the present eyetracking experiment, we tested the hypothesis that the efficiency of word recognition during reading improves with increases in print exposure, by determining whether the magnitude of the repetition-priming effect is modulated by individual differences in scores on the author recognition test (ART). Lexical repetition of target words was manipulated across pairs of unrelated sentences that were presented on consecutive trials. The magnitude of the repetition effect was modulated by print exposure in early measures of processing, such that the magnitude of the effect was inversely related to scores on the ART. The results showed that low levels of print exposure, and thus lower-quality lexical representations, are associated with high levels of difficulty recognizing words, and thus with the greatest room to benefit from repetition. Furthermore, the interaction between scores on the ART and repetition suggests that print exposure is not simply an index of general reading speed, but rather that higher levels of print exposure are associated with an enhanced ability to access lexical knowledge and recognize words during reading.

Exact and conceptual repetition dissociate conceptual memory tests: problems for transfer appropriate processing theory.

PubMed

McDermott, K B; Roediger, H L

1996-03-01

Three experiments examined whether a conceptual implicit memory test (specifically, category instance generation) would exhibit repetition effects similar to those found in free recall. The transfer appropriate processing account of dissociations among memory tests led us to predict that the tests would show parallel effects; this prediction was based upon the theory's assumption that conceptual tests will behave similarly as a function of various independent variables. In Experiment 1, conceptual repetition (i.e., following a target word [e.g., puzzles] with an associate [e.g., jigsaw]) did not enhance priming on the instance generation test relative to the condition of simply presenting the target word once, although this manipulation did affect free recall. In Experiment 2, conceptual repetition was achieved by following a picture with its corresponding word (or vice versa). In this case, there was an effect of conceptual repetition on free recall but no reliable effect on category instance generation or category cued recall. In addition, we obtained a picture superiority effect in free recall but not in category instance generation. In the third experiment, when the same study sequence was used as in Experiment 1, but with instructions that encouraged relational processing, priming on the category instance generation task was enhanced by conceptual repetition. Results demonstrate that conceptual memory tests can be dissociated and present problems for Roediger's (1990) transfer appropriate processing account of dissociations between explicit and implicit tests.

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.

Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning

DOE PAGES

Sanchez-Gonzalez, A.; Micaelli, P.; Olivier, C.; ...

2017-06-05

Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy,more » we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. Lastly, this opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.« less

Accurate prediction of X-ray pulse properties from a free-electron laser using machine learning

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

Sanchez-Gonzalez, A.; Micaelli, P.; Olivier, C.

Free-electron lasers providing ultra-short high-brightness pulses of X-ray radiation have great potential for a wide impact on science, and are a critical element for unravelling the structural dynamics of matter. To fully harness this potential, we must accurately know the X-ray properties: intensity, spectrum and temporal profile. Owing to the inherent fluctuations in free-electron lasers, this mandates a full characterization of the properties for each and every pulse. While diagnostics of these properties exist, they are often invasive and many cannot operate at a high-repetition rate. Here, we present a technique for circumventing this limitation. Employing a machine learning strategy,more » we can accurately predict X-ray properties for every shot using only parameters that are easily recorded at high-repetition rate, by training a model on a small set of fully diagnosed pulses. Lastly, this opens the door to fully realizing the promise of next-generation high-repetition rate X-ray lasers.« less

Diagnostic for a high-repetition rate electron photo-gun and first measurements

NASA Astrophysics Data System (ADS)

Filippetto, D.; Doolittle, L.; Huang, G.; Norum, E.; Portmann, G.; Qian, H.; Sannibale, F.

2015-05-01

The APEX electron source at LBNL combines the high-repetition-rate with the high beam brightness typical of photoguns, delivering low emittance electron pulses at MHz frequency. Proving the high beam quality of the beam is an essential step for the success of the experiment, opening the doors of the high average power to brightness-hungry applications as X-Ray FELs, MHz ultrafast electron diffraction etc.. As first step, a complete characterization of the beam parameters is foreseen at the Gun beam energy of 750 keV. Diagnostics for low and high current measurements have been installed and tested, and measurements of cathode lifetime and thermal emittance in a RF environment with mA current performed. The recent installation of a double slit system, a deflecting cavity and a high precision spectrometer, allow the exploration of the full 6D phase space. Here we discuss the present layout of the machine and future upgrades, showing the latest results at low and high repetition rate, together with the tools and techniques used.

Fabrication of embedded microball lens in PMMA with high repetition rate femtosecond fiber laser.

PubMed

Zheng, Chong; Hu, Anming; Li, Ruozhou; Bridges, Denzel; Chen, Tao

2015-06-29

Embedded microball lenses with superior optical properties function as convex microball lens (VMBL) and concave microball lens (CMBL) were fabricated inside a PMMA substrate with a high repetition rate femtosecond fiber laser. The VMBL was created by femtosecond laser-induced refractive index change, while the CMBL was fabricated due to the heat accumulation effect of the successive laser pulses irradiation at a high repetition rate. The processing window for both types of the lenses was studied and optimized, and the optical properties were also tested by imaging a remote object with an inverted microscope. In order to obtain the microball lenses with adjustable focal lengths and suppressed optical aberration, a shape control method was thus proposed and examined with experiments and ZEMAX® simulations. Applying the optimized fabrication conditions, two types of the embedded microball lenses arrays were fabricated and then tested with imaging experiments. This technology allows the direct fabrication of microlens inside transparent bulk polymer material which has great application potential in multi-function integrated microfluidic devices.

Research on the liquid coolant applied in the high repetition rate slab amplifier

NASA Astrophysics Data System (ADS)

Wang, Bingyan; Li, Yangshuai; Zhang, Panzheng; Wang, Li; Zhang, Yanli; Feng, Tao; Zhou, Qiong; Liu, Qiang; Li, Haiyuan; Zhang, Xu; Zhou, Shenlei; Ma, Weixin; Zhu, Jian; Zhu, Jianqiang

2018-03-01

High repetition rate slab amplifier (HRRSA) is extraordinarily indispensable for the future fusion power plant, ultra-short laser, laser weapon, and so on. Thermal controlling is the decisive factor for the repetition rate and the output energy of the slab amplifier. For larger clear aperture HRRSA, flash-lamp pumped slab amplifier based on neodymium phosphate glass (Nd:glass) is chosen with the liquid cooling. The liquid coolant circulates across the Nd:glass and takes off the thermal induced in the pumping process. A novel liquid coolant (Series A) whose refractive index is the same with Nd:glass is proposed to alleviate the wavefront distortion induced by thermal. The chemical stability of the liquid coolant under high energy flash-lamp irradiation with 200 shots and under the irradiation of a 1053nm laser with 19 hours and 37 hours are experimented. The results show that the chemical stability of the liquid coolant is stable under irradiation.

A smart repetitive-rate wideband high power microwave source

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

Li, Wei; Zhang, Jun; Qian, Bao-liang

2016-01-15

A smart repetitive-rate wideband High Power Microwave (HPM) source based on the A6 Magnetron with Diffraction Output is described in this paper. The length of the HPM source is 30 cm and its weight is 35 kg. Computer simulations show that the source can produce microwave with central frequency of 1.91 GHz and bandwidth of about 11%. Experimental measurements show that the output microwave power from the source reaches in maximum 110 MW when the input electric power from the pulsed driver is ∼500 MW, which gives the power conversion efficiency 22%. Central frequency of the output HPM in the experiment is 1.94 GHz withmore » the bandwidth ranging from 1.82 GHz to 2.02 GHz. The jitter of the output HPM power is lower than 3 dB when the source operates in the repetition mode with 50 Hz rate.« less

A low timing jitter picosecond microchip laser pumped by pulsed LD

NASA Astrophysics Data System (ADS)

Wang, Sha; Wang, Yan-biao; Feng, Guoying; Zhou, Shou-huan

2016-07-01

SESAM passively Q-switched microchip laser is a very promising instrument to replace mode locked lasers to obtain picosecond pulses. The biggest drawback of a passively Q-switched microchip laser is its un-avoided large timing jitter, especially when the pump intensity is low, i.e. at low laser repetition rate range. In order to obtain a low timing jitter passively Q-switched picosecond microchip laser in the whole laser repetition rate range, a 1000 kHz pulsed narrow bandwidth Fiber Bragg Grating (FBG) stablized laser diode was used as the pump source. By tuning the pump intensity, we could control the output laser frequency. In this way, we achieved a very low timing jitter passively Q-switched picosecond laser at 2.13 mW, 111.1 kHz. The relative timing jitter was only 0.0315%, which was around 100 times smaller compared with a cw LD pumped microchip working at hundred kilohertz repetition rate frequency range.

Indigenous Students' Increasing Risk of Grade Repetition in Early Schooling

ERIC Educational Resources Information Center

Anderson, Robyn

2012-01-01

The current study considers grade repetition rates in the early years of school, Preparatory (Prep) to Year 3, in Queensland state schools, of which there is a significant gap in the Australian research literature. Data accessed from the Queensland Government's Department of Education and Training (DET), shows that particular groups of students…

High-power pulse repetitive HF(DF) laser with a solid-state pump generator

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

Velikanov, S D; Domazhirov, A P; Zaretskiy, N A

2015-11-30

Operation of a repetitively pulsed electric-discharge HF(DF) laser with an all-solid-state pump generator based on FID switches is demonstrated. The energy stored in the pump generator capacitors was 880 J at an open-circuit voltage of 240 kV and a discharge pulse repetition rate of 25 Hz. The specific energy extractions were 3.8 and 3.4 J L{sup -1} for the HF and DF lasers, respectively. The possibilities of improving the output laser characteristics are discussed. (lasers)

Note: All solid-state high repetitive sub-nanosecond risetime pulse generator based on bulk gallium arsenide avalanche semiconductor switches.

PubMed

Hu, Long; Su, Jiancang; Ding, Zhenjie; Hao, Qingsong; Fan, Yajun; Liu, Chunliang

2016-08-01

An all solid-state high repetitive sub-nanosecond risetime pulse generator featuring low-energy-triggered bulk gallium arsenide (GaAs) avalanche semiconductor switches and a step-type transmission line is presented. The step-type transmission line with two stages is charged to a potential of 5.0 kV also biasing at the switches. The bulk GaAs avalanche semiconductor switch closes within sub-nanosecond range when illuminated with approximately 87 nJ of laser energy at 905 nm in a single pulse. An asymmetric dipolar pulse with peak-to-peak amplitude of 9.6 kV and risetime of 0.65 ns is produced on a resistive load of 50 Ω. A technique that allows for repetition-rate multiplication of pulse trains experimentally demonstrated that the parallel-connected bulk GaAs avalanche semiconductor switches are triggered in sequence. The highest repetition rate is decided by recovery time of the bulk GaAs avalanche semiconductor switch, and the operating result of 100 kHz of the generator is discussed.

Design and development of repetitive capacitor charging power supply based on series-parallel resonant converter topology.

PubMed

Patel, Ankur; Nagesh, K V; Kolge, Tanmay; Chakravarthy, D P

2011-04-01

LCL resonant converter based repetitive capacitor charging power supply (CCPS) is designed and developed in the division. The LCL converter acts as a constant current source when switching frequency is equal to the resonant frequency. When both resonant inductors' values of LCL converter are same, it results in inherent zero current switching (ZCS) in switches. In this paper, ac analysis with fundamental frequency approximation of LCL resonant tank circuit, frequency dependent of current gain converter followed by design, development, simulation, and practical result is described. Effect of change in switching frequency and resonant frequency and change in resonant inductors ratio on CCPS will be discussed. An efficient CCPS of average output power of 1.2 kJ/s, output voltage 3 kV, and 300 Hz repetition rate is developed in the division. The performance of this CCPS has been evaluated in the laboratory by charging several values of load capacitance at various repetition rates. These results indicate that this design is very feasible for use in capacitor-charging applications. © 2011 American Institute of Physics

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, Emanuel M.

1987-01-01

A high-power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, E.M.

1984-06-05

A high power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime.

Examining impairment of adaptive compensation for stabilizing motor repetitions in stroke survivors.

PubMed

Kim, Yushin; Koh, Kyung; Yoon, BumChul; Kim, Woo-Sub; Shin, Joon-Ho; Park, Hyung-Soon; Shim, Jae Kun

2017-12-01

The hand, one of the most versatile but mechanically redundant parts of the human body, suffers more and longer than other body parts after stroke. One of the rehabilitation paradigms, task-oriented rehabilitation, encourages motor repeatability, the ability to produce similar motor performance over repetitions through compensatory strategies while taking advantage of the motor system's redundancy. The previous studies showed that stroke survivors inconsistently performed a given motor task with limited motor solutions. We hypothesized that stroke survivors would exhibit deficits in motor repeatability and adaptive compensation compared to healthy controls in during repetitive force-pulse (RFP) production tasks using multiple fingers. Seventeen hemiparetic stroke survivors and seven healthy controls were asked to repeatedly press force sensors as fast as possible using the four fingers of each hand. The hierarchical variability decomposition model was employed to compute motor repeatability and adaptive compensation across finger-force impulses, respectively. Stroke survivors showed decreased repeatability and adaptive compensation of force impulses between individual fingers as compared to the control (p < 0.05). The stroke survivors also showed decreased pulse frequency and greater peak-to-peak time variance than the control (p < 0.05). Force-related variables, such as mean peak force and peak force interval variability, demonstrated no significant difference between groups. Our findings indicate that stroke-induced brain injury negatively affects their ability to exploit their redundant or abundant motor system in an RFP task.

Does practicing a wide range of joint angle configurations lead to higher flexibility in a manual obstacle-avoidance target-pointing task?

PubMed Central

Bootsma, Reinoud J.; Schoemaker, Marina M.; Otten, Egbert; Mouton, Leonora J.; Bongers, Raoul M.

2017-01-01

Flexibility in motor actions can be defined as variability in the use of degrees of freedom (e.g., joint angles in the arm) over repetitions while keeping performance (e.g., fingertip position) stabilized. We examined whether flexibility can be increased through enlarging the joint angle range during practice in a manual obstacle-avoidance target-pointing task. To establish differences in flexibility we partitioned the variability in joint angles over repetitions in variability within (GEV) and variability outside the solution space (NGEV). More GEV than NGEV reflects flexibility; when the ratio of the GEV and NGEV is higher, flexibility is higher. The pretest and posttest consisted of 30 repetitions of manual pointing to a target while moving over a 10 cm high obstacle. To enlarge the joint angle range during practice participants performed 600 target-pointing movements while moving over obstacles of different heights (5–9 cm, 11–15 cm). The results indicated that practicing movements over obstacles of different heights led participants to use enlarged range of joint angles compared to the range of joint angles used in movements over the 10 cm obstacle in the pretest. However, for each individual obstacle neither joint angle variance nor flexibility were higher during practice. We also did not find more flexibility after practice. In the posttest, joint angle variance was in fact smaller than before practice, primarily in GEV. The potential influences of learning effects and the task used that could underlie the results obtained are discussed. We conclude that with this specific type of practice in this specific task, enlarging the range of joint angles does not lead to more flexibility. PMID:28700695

Effects of shifts in the rate of repetitive stimulation on sustained attention

NASA Technical Reports Server (NTRS)

Krulewitz, J. E.; Warm, J. S.; Wohl, T. H.

1975-01-01

The effects of shifts in the rate of presentation of repetitive neutral events (background event rate) were studied in a visual vigilance task. Four groups of subjects experienced either a high (21 events/min) or a low (6 events/min) event rate for 20 min and then experienced either the same or the alternate event rate for an additional 40 min. The temporal occurrence of critical target signals was identical for all groups, irrespective of event rate. The density of critical signals was 12 signals/20 min. By the end of the session, shifts in event rate were associated with changes in performance which resembled contrast effects found in other experimental situations in which shift paradigms were used. Relative to constant event rate control conditions, a shift from a low to a high event rate depressed the probability of signal detections, while a shift in the opposite direction enhanced the probability of signal detections.

Increased repetitive behaviours and prolactin responsivity to oral m-chlorophenylpiperazine in adults with autism spectrum disorders.

PubMed

Novotny, Sherie; Hollander, Eric; Phillips, Ann; Allen, Andrea; Wasserman, Stacey; Iyengar, Rupa

2004-09-01

Autism is a neurodevelopmental disorder characterized by dysfunction in three primary behavioural domains: repetitive behaviours, social deficits, and language abnormalities. There is evidence that abnormalities exist in the serotonin (5-HT) system in autism spectrum patients. Furthermore, 5-HT is known to play a role in repetitive and social behaviours. This study examined the effect of m-chlorophenylpiperazine (m-CPP) on repetitive behaviours and prolactin response in 11 adults with autism or Aspergers disorder and 8 age- and gender-matched healthy controls via randomized double-blind, m-CPP and placebo challenges. The primary outcome measure was an instrument rating six repetitive behaviours: need to know, repeating, ordering, need to tell/ask, self-injury, and touching. Patients with autism spectrum disorders showed a significant increase in repetitive behaviours at end-point following oral m-CPP in comparison to placebo. Additionally subjects with autism spectrum disorders showed a significantly increased prolactin response to m-CPP compared to normal controls, with neither group responding to placebo. This study provides further evidence for altered 5-HT sensitivity in individuals with autism spectrum disorders, as well as a possible relationship between repetitive behaviours in autism spectrum disorders and abnormalities in the 5-HT system.

Foot strike and injury rates in endurance runners: a retrospective study.

PubMed

Daoud, Adam I; Geissler, Gary J; Wang, Frank; Saretsky, Jason; Daoud, Yahya A; Lieberman, Daniel E

2012-07-01

This retrospective study tests if runners who habitually forefoot strike have different rates of injury than runners who habitually rearfoot strike. We measured the strike characteristics of middle- and long-distance runners from a collegiate cross-country team and quantified their history of injury, including the incidence and rate of specific injuries, the severity of each injury, and the rate of mild, moderate, and severe injuries per mile run. Of the 52 runners studied, 36 (69%) primarily used a rearfoot strike and 16 (31%) primarily used a forefoot strike. Approximately 74% of runners experienced a moderate or severe injury each year, but those who habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike. Traumatic injury rates were not significantly different between the two groups. A generalized linear model showed that strike type, sex, race distance, and average miles per week each correlate significantly (P < 0.01) with repetitive injury rates. Competitive cross-country runners on a college team incur high injury rates, but runners who habitually rearfoot strike have significantly higher rates of repetitive stress injury than those who mostly forefoot strike. This study does not test the causal bases for this general difference. One hypothesis, which requires further research, is that the absence of a marked impact peak in the ground reaction force during a forefoot strike compared with a rearfoot strike may contribute to lower rates of injuries in habitual forefoot strikers.

Single and Multi-Pulse Low-Energy Conical Theta Pinch Inductive Pulsed Plasma Thruster Performance

NASA Technical Reports Server (NTRS)

Hallock, A. K.; Martin, A. K.; Polzin, K. A.; Kimberlin, A. C.; Eskridge, R. H.

2013-01-01

Impulse bits produced by conical theta-pinch inductive pulsed plasma thrusters possessing cone angles of 20deg, 38deg, and 60deg, were quantified for 500J/pulse operation by direct measurement using a hanging-pendulum thrust stand. All three cone angles were tested in single-pulse mode, with the 38deg model producing the highest impulse bits at roughly 1 mN-s operating on both argon and xenon propellants. A capacitor charging system, assembled to support repetitively-pulsed thruster operation, permitted testing of the 38deg thruster at a repetition-rate of 5 Hz at power levels of 0.9, 1.6, and 2.5 kW. The average thrust measured during multiple-pulse operation exceeded the value obtained when the single-pulse impulse bit is multiplied by the repetition rate.

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

Walters, C.T.; Dulaney, J.L.; Campbell, B.E.

Demonstrations of operation of a compact neodymium glass laser with average output powers greater than 1 kW for several seconds are reported. The laser is based on the thermal inertia laser (TIL) concept wherein a neodymium-doped glass rod is pumped uniformly without cooling during a burst mode of laser operation. Design principles for TIL devices and scaling to 100 kW class lasers are discussed. Experimental results for a low repetition-rate proof-of-concept pulsed device (30 J, 0.2 Hz) and a high repetition-rate pulsed prototype (40 J, 36 Hz) are presented and compared to numerical solutions for the laser rate equations withmore » temperature dependent cross-sections.« less

Contrasting the Chromosomal Organization of Repetitive DNAs in Two Gryllidae Crickets with Highly Divergent Karyotypes

PubMed Central

Palacios-Gimenez, Octavio M.; Carvalho, Carlos Roberto; Ferrari Soares, Fernanda Aparecida; Cabral-de-Mello, Diogo C.

2015-01-01

A large percentage of eukaryotic genomes consist of repetitive DNA that plays an important role in the organization, size and evolution. In the case of crickets, chromosomal variability has been found using classical cytogenetics, but almost no information concerning the organization of their repetitive DNAs is available. To better understand the chromosomal organization and diversification of repetitive DNAs in crickets, we studied the chromosomes of two Gryllidae species with highly divergent karyotypes, i.e., 2n(♂) = 29,X0 (Gryllus assimilis) and 2n = 9, neo-X1X2Y (Eneoptera surinamensis). The analyses were performed using classical cytogenetic techniques, repetitive DNA mapping and genome-size estimation. Conserved characteristics were observed, such as the occurrence of a small number of clusters of rDNAs and U snDNAs, in contrast to the multiple clusters/dispersal of the H3 histone genes. The positions of U2 snDNA and 18S rDNA are also conserved, being intermingled within the largest autosome. The distribution and base-pair composition of the heterochromatin and repetitive DNA pools of these organisms differed, suggesting reorganization. Although the microsatellite arrays had a similar distribution pattern, being dispersed along entire chromosomes, as has been observed in some grasshopper species, a band-like pattern was also observed in the E. surinamensis chromosomes, putatively due to their amplification and clustering. In addition to these differences, the genome of E. surinamensis is approximately 2.5 times larger than that of G. assimilis, which we hypothesize is due to the amplification of repetitive DNAs. Finally, we discuss the possible involvement of repetitive DNAs in the differentiation of the neo-sex chromosomes of E. surinamensis, as has been reported in other eukaryotic groups. This study provided an opportunity to explore the evolutionary dynamics of repetitive DNAs in two non-model species and will contribute to the understanding of chromosomal evolution in a group about which little chromosomal and genomic information is known. PMID:26630487

Contrasting the Chromosomal Organization of Repetitive DNAs in Two Gryllidae Crickets with Highly Divergent Karyotypes.

PubMed

Palacios-Gimenez, Octavio M; Carvalho, Carlos Roberto; Ferrari Soares, Fernanda Aparecida; Cabral-de-Mello, Diogo C

2015-01-01

A large percentage of eukaryotic genomes consist of repetitive DNA that plays an important role in the organization, size and evolution. In the case of crickets, chromosomal variability has been found using classical cytogenetics, but almost no information concerning the organization of their repetitive DNAs is available. To better understand the chromosomal organization and diversification of repetitive DNAs in crickets, we studied the chromosomes of two Gryllidae species with highly divergent karyotypes, i.e., 2n(♂) = 29,X0 (Gryllus assimilis) and 2n = 9, neo-X1X2Y (Eneoptera surinamensis). The analyses were performed using classical cytogenetic techniques, repetitive DNA mapping and genome-size estimation. Conserved characteristics were observed, such as the occurrence of a small number of clusters of rDNAs and U snDNAs, in contrast to the multiple clusters/dispersal of the H3 histone genes. The positions of U2 snDNA and 18S rDNA are also conserved, being intermingled within the largest autosome. The distribution and base-pair composition of the heterochromatin and repetitive DNA pools of these organisms differed, suggesting reorganization. Although the microsatellite arrays had a similar distribution pattern, being dispersed along entire chromosomes, as has been observed in some grasshopper species, a band-like pattern was also observed in the E. surinamensis chromosomes, putatively due to their amplification and clustering. In addition to these differences, the genome of E. surinamensis is approximately 2.5 times larger than that of G. assimilis, which we hypothesize is due to the amplification of repetitive DNAs. Finally, we discuss the possible involvement of repetitive DNAs in the differentiation of the neo-sex chromosomes of E. surinamensis, as has been reported in other eukaryotic groups. This study provided an opportunity to explore the evolutionary dynamics of repetitive DNAs in two non-model species and will contribute to the understanding of chromosomal evolution in a group about which little chromosomal and genomic information is known.

Deliberate self harm: systematic review of efficacy of psychosocial and pharmacological treatments in preventing repetition

PubMed Central

Hawton, Keith; Arensman, Ella; Townsend, Ellen; Bremner, Sandy; Feldman, Eleanor; Goldney, Robert; Gunnell, David; Hazell, Philip; van Heeringen, Kees; House, Allan; Owens, David; Sakinofsky, Isaac; Träskman-Bendz, Lil

1998-01-01

Objective: To identify and synthesise the findings from all randomised controlled trials that have examined the effectiveness of treatments of patients who have deliberately harmed themselves. Design: Systematic review of randomised controlled trials of psychosocial and physical treatments. Studies categorised according to type of treatment. When there was more than one investigation in a particular category a summary odds ratio was estimated with the Mantel-Haenszel method. Setting: Randomised trials available in electronic databases in 1996, in the Cochrane Controlled Trials Register in 1997, and from hand searching of journals to 1997. Subjects: Patients who had deliberately harmed themselves shortly before entry into the trials with information on repetition of behaviour. The included trials comprised 2452 randomised participants with outcome data. Main outcome measure: Repetition of self harm. Results: 20 trials reported repetition of self harm as an outcome variable, classified into 10 categories. Summary odds ratio (all for comparison with standard aftercare) indicated reduced repetition for problem solving therapy (0.73; 95% confidence interval 0.45 to 1.18) and for provision of an emergency contact card in addition to standard care (0.45; 0.19 to 1.07). The summary odds ratios were 0.83 (0.61 to 1.14) for trials of intensive aftercare plus outreach and 1.19 (0.53 to 2.67) for antidepressant treatment compared with placebo. Significantly reduced rates of further self harm were observed for depot flupenthixol versus placebo in multiple repeaters (0.09; 0.02 to 0.50) and for dialectical behaviour therapy versus standard aftercare (0.24; 0.06 to 0.93). Conclusion: There remains considerable uncertainty about which forms of psychosocial and physical treatments of patients who harm themselves are most effective. Further larger trials of treatments are needed. Key messages A systematic review of the effectiveness of psychosocial and drug treatments of patients who deliberately harm themselves identified 20 randomised controlled trials in which repetition of self harm was reported as an outcome Promising results were found for problem solving therapy, provision of a card to allow patients to make emergency contact with services, depot flupenthixol for recurrent self harm, and long term psychological therapy for female patients with borderline personality disorder and recurrent self harm Assertive outreach can help to keep patients in treatment Nearly all the trials included too few patients to detect clinically significant differences in repetition of self harm, and even synthesis of results by meta-analysis did not have the power to detect such differences There is an urgent need for large trials of promising therapies for this substantial clinical population PMID:9703526

Wright Laboratory Research and Development Facilities Handbook

DTIC Science & Technology

1992-08-01

properties o. superconductors SPECIAL/UNIQUE CAPABILITIES: Two superconducting coils: 3-inch bore, 10 Tesla coil. 20 kilojoule repetitively pulsed coil 7 inch...bore, cryogenically cooled 14 Tesla coil INSTRUMENTATION: Computer Controlled Variable Temperature (2-400K) and Field (0-5 Tesla ) Squid Susceptometer...Variable Temperature (10-80K) and Field (0-10 Tesla ) Transport Current Measurement Apparatus RF Source Sputtering Rig, Optical Microscope, Furnaces

The Use of a Discrimination-Training Procedure to Teach Mand Variability to Children with Autism

ERIC Educational Resources Information Center

Brodhead, Matthew T.; Higbee, Thomas S.; Gerencser, Kristina R.; Akers, Jessica S.

2016-01-01

We investigated the effects of a script-fading and discrimination-training procedure on mand variability in preschoolers with autism. Participants were taught to vary their vocal mands in the presence of written scripts, a green placemat, and a lag schedule of reinforcement. They were also taught to engage in repetitive mands in the presence of…

Repetitive flash x-ray generator operated at low-dose rates for a medical x-ray television system

NASA Astrophysics Data System (ADS)

Sato, Eiichi; Isobe, Hiroshi; Takahashi, Kei; Tamakawa, Yoshiharu; Yanagisawa, Toru

1991-04-01

The fundamental studies for the repetitive flash x-ray generator operated at lowdose rates for a medical x-ray television system are described. This x-ray generator consisted of the following components: a high-voltage power supply, an energy storage condenser of lOOnF, a coaxial cable condenser with a capacity of l000pF, a repetitive impulse switching system, a turbo molecular pump, and an x-ray tube having a cold cathode. The condenser was charged from 40 to 70kV by a power supply, and the electric charges stored in the condenser were discharged repetitively by using a trigger electrode operated by an impulse switching system. The x-ray tube was of the triode-type which was connected to the turbo molecular pump and had a large discharge impedance in order to prevent the damped oscillations of the tube current and voltage. The maximum tube voltage was equivalent to the initial charged voltage, and the peak current was less than 70A. The durations were about 2ps, and the x-ray intensities were less than 1. OpC/kg at 0. 5m per pulse. The repetition frequency was less than 50Hz, and the effective focal spot size was equivalent to the anode diameter of 3. 0mm. For the x-ray television system used in conjunction with this repetitive pulsed x-ray generator, since the electromagnetic noise primarily caused by the high tube current was decreased, noise-free stroboscopic radiography performed by the television system could be realized.

Meaningful Words and Non-Words Repetitive Articulatory Rate (Oral Diadochokinesis) in Persian Speaking Children.

PubMed

Zamani, Peyman; Rezai, Hossein; Garmatani, Neda Tahmasebi

2017-08-01

Repetitive articulatory rate or Oral Diadochokinesis (oral-DDK) shows a guideline for appraisal and diagnosis of subjects with oral-motor disorder. Traditionally, meaningless words repetition has been utilized in this task and preschool children have challenges with them. Therefore, we aimed to determine some meaningful words in order to test oral-DDK in Persian speaking preschool children. Participants were 142 normally developing children, (age range 4-6 years), who were asked to produce /motæka, golabi/ as two meaningful Persian words and /pa-ta-ka/ as non-word in conventional oral-DDK task. We compared the time taken for 10-times fast repetitions of two meaningful Persian words and the tri-syllabic nonsense word /pa-ta-ka/. Praat software was used to calculate the average time that subjects took to produce the target items. In 4-5 year old children, [Formula: see text] of time taken for 10-times repetitions of /pa-ta-ka, motæka, golabi/ were [Formula: see text], and [Formula: see text] seconds respectively, and in 5-6 year old children were [Formula: see text], and [Formula: see text] seconds respectively. Findings showed that the main effect of type of words on oral diadochokinesis was significant ([Formula: see text]). Children repeated meaningful words /motæka, golabi/ faster than the non-word /pa-ta-ka/. Sex and age factors had no effect on time taken for repetition of oral-DDK test. It is suggested that Speech Therapists can use meaningful words to facilitate oral-DDK test for children.

Dependence of vestibular reactions on frequency of action of sign-variable accelerations

NASA Technical Reports Server (NTRS)

Lapayev, E. V.; Vorobyev, O. A.; Ivanov, V. V.

1980-01-01

It was revealed that during the tests with continuous action of sign variable Coriolis acceleration the development of kinetosis was proportionate to the time of head inclinations in the range of 1 to 4 seconds while illusions of rocking in sagittal plane was more expressed in fast inclinations. The obtained data provided the evidence of sufficient dependence of vestibulovegetative and vestibulosensory reactions on the period of repetition of sign variable Coriolis acceleration.

A proof-of-concept study on the combination of repetitive transcranial magnetic stimulation and relaxation techniques in chronic tinnitus.

PubMed

Kreuzer, Peter M; Poeppl, Timm B; Bulla, Jan; Schlee, Winfried; Lehner, Astrid; Langguth, Berthold; Schecklmann, Martin

2016-10-01

Interference of ongoing neuronal activity and brain stimulation motivated this study to combine repetitive transcranial magnetic stimulation (rTMS) and relaxation techniques in tinnitus patients. Forty-two patients were enrolled in this one-arm proof-of-concept study to receive ten sessions of rTMS applied to the left dorsolateral prefrontal cortex and temporo-parietal cortex. During stimulation, patients listened to five different kinds of relaxation audios. Variables of interest were tinnitus questionnaires, tinnitus numeric rating scales, depressivity, and quality of life. Results were compared to results of historical control groups having received the same rTMS protocol (active control) and sham treatment (placebo) without relaxation techniques. Thirty-eight patients completed the treatment, drop-out rates and adverse events were low. Responder rates (reduction in tinnitus questionnaire (TQ) score ≥5 points 10 weeks after treatment) were 44.7 % in the study, 27.8 % in the active control group, and 21.7 % in the placebo group, differing between groups on a near significant level. For the tinnitus handicap inventory (THI), the main effect of group was not significant. However, linear mixed model analyses showed that the relaxation/rTMS group differed significantly from the active control group showing steeper negative THI trend for the relaxation/rTMS group indicating better amelioration over the course of the trial. Deepness of relaxation during rTMS and selection of active relaxation vs. passive listening to music predicted larger TQ. All remaining secondary outcomes turned out non-significant. This combined treatment proved to be a safe, feasible and promising approach to enhance rTMS treatment effects in chronic tinnitus.

The Importance of Movement Velocity as a Measure to Control Resistance Training Intensity

PubMed Central

González-Badillo, Juan J.; Marques, Mário C.; Sánchez-Medina, Luis

2011-01-01

Configuration of the exercise stimulus in resitance training has been traditionally associated with a combination of the so-called ‘acute resistance exercise variables’ (exercise type and order, loading, number of repetitions and sets, rests duration and movement velocity). During typical resistance exercise in isoinertial conditions, and assuming every repetition is performed with maximal voluntary effort, velocity unintentionally declines as fatigue develops. However, few studies analyzing the response to different resitance training schemes have described changes in repetition velocity or power. It thus seems necessary to conduct more research using models of fatigue that analyze the reduction in mechanical variables such as force, velocity and power output over repeated dynamic contractions in actual training or competition settings. Thus, the aim of this paper was to discuss the importance of movement velocity concerning control training intensity. PMID:23487504

Note: Simple 100 Hz N2 laser with longitudinal discharge tube and high-voltage power supply using neon sign transformer.

PubMed

Uno, K; Jitsuno, T

2017-12-01

We developed a longitudinally excited N 2 laser with a simple driver circuit and a simple power supply. The N 2 laser consisted of a 20 cm-long glass tube with an inner diameter of 2.5 mm, a normal stable resonator formed by flat mirrors, a variable transformer, a neon sign transformer, a spark gap, and a 200 pF capacitance. The N 2 laser produced a laser pulse with an energy of 379 nJ and a pulse width of 7.5 ns at a repetition rate of 100 Hz. The laser beam was circular and had a Gaussian profile with a correlation factor of 0.992 93.

Should helicopter noise be measured differently from other aircraft noise? A review of the psychoacoustic literature

NASA Technical Reports Server (NTRS)

Molino, J. A.

1982-01-01

A review of 34 studies indicates that several factors or variables might be important in providing a psychoacoustic foundation for measurements of the noise from helicopters. These factors are phase relations, tail rotor noise, repetition rate, crest level, and generic differences between conventional aircraft and helicopters. Particular attention was given to the impulsive noise known as blade slap. Analysis of the evidence for and against each factor reveals that, for the present state of scientific knowledge, none of these factors should be regarded as the basis for a significant noise measurement correction due to impulsive blade slap. The current method of measuring effective perceived noise level for conventional aircraft appears to be adequate for measuring helicopter noise as well.

Pulsed and cw laser oscillations in LiF:F-2 color center crystal under laser diode pumping.

PubMed

Basiev, Tasoltan T; Vassiliev, Sergey V; Konjushkin, Vasily A; Gapontsev, Valentin P

2006-07-15

Continuous-wave laser oscillations in LiF:F-2 crystal optically pumped by a laser diode at 970 nm were demonstrated for what is believed to be the first time. The slope efficiency of 14% and conversion efficiency of 5.5% were achieved for 80 micros pump pulse duration and 5 Hz pulse repetition rate. An efficiency twice as low was measured at a 6.25 kHz pulse repetition rate (50% off-duty factor) and in cw mode of laser operation.

High energy passively mode-locked erbium-doped fiber laser at tens of kHz repetition rate

NASA Astrophysics Data System (ADS)

Chen, Jiong; Jia, Dongfang; Wang, Changle; Wang, Junlong; Wang, Zhaoying; Yang, Tianxin

2011-12-01

We demonstrate an ultra-long cavity all-fiber Erbium-doped fiber laser that is passively mode-locked by nonlinear polarization rotation. The length of the resonant cavity amounts to 4.046 km, which is achieved by incorporating a 4 km single mode fiber. The laser generates stable mode-locked pulses with a 50.90 kHz fundamental repetition rate. The maximum average power of output pulses is 2.73 mW, which corresponds to per-pulse energy of 53.63 nJ.

Ultrafast electron diffraction with megahertz MeV electron pulses from a superconducting radio-frequency photoinjector

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

Feng, L. W.; Lin, L.; Huang, S. L.

We report ultrafast relativistic electron diffraction operating at the megahertz repetition rate where the electron beam is produced in a superconducting radio-frequency (rf) photoinjector. We show that the beam quality is sufficiently high to provide clear diffraction patterns from gold and aluminium samples. With the number of electrons, several orders of magnitude higher than that from a normal conducting photocathode rf gun, such high repetition rate ultrafast MeV electron diffraction may open up many new opportunities in ultrafast science.

Molecular dynamics study of lubricant depletion by pulsed laser heating

NASA Astrophysics Data System (ADS)

Seo, Young Woo; Rosenkranz, Andreas; Talke, Frank E.

2018-05-01

In this study, molecular dynamics simulations were performed to numerically investigate the effect of pulsed laser heating on lubricant depletion. The maximum temperature, the lubricant depletion width, the number of evaporated lubricant beads and the number of fragmented lubricant chains were studied as a function of laser peak power, pulse duration and repetition rate. A continuous-wave laser and a square pulse laser were simulated and compared to a Gaussian pulse laser. With increasing repetition rate, pulsed laser heating was found to approach continuous-wave laser heating.

Nonword Repetition by Children with Cochlear Implants: Accuracy Ratings from Normal-Hearing Listeners.

ERIC Educational Resources Information Center

Dillon, Caitlin M.; Burkholder, Rose A.; Cleary, Miranda; Pisoni, David B.

2004-01-01

Seventy-six children with cochlear implants completed a nonword repetition task. The children were presented with 20 nonword auditory patterns over a loudspeaker and were asked to repeat them aloud to the experimenter. The children's responses were recorded on digital audiotape and then played back to normal-hearing adult listeners to obtain…

Versatile photonic microwave waveforms generation using a dual-parallel Mach-Zehnder modulator without other dispersive elements

NASA Astrophysics Data System (ADS)

Bai, Guang-Fu; Hu, Lin; Jiang, Yang; Tian, Jing; Zi, Yue-Jiao; Wu, Ting-Wei; Huang, Feng-Qin

2017-08-01

In this paper, a photonic microwave waveform generator based on a dual-parallel Mach-Zehnder modulator is proposed and experimentally demonstrated. In this reported scheme, only one radio frequency signal is used to drive the dual-parallel Mach-Zehnder modulator. Meanwhile, dispersive elements or filters are not required in the proposed scheme, which make the scheme simpler and more stable. In this way, six variables can be adjusted. Through the different combinations of these variables, basic waveforms with full duty and small duty cycle can be generated. Tunability of the generator can be achieved by adjusting the frequency of the RF signal and the optical carrier. The corresponding theoretical analysis and simulation have been conducted. With guidance of theory and simulation, proof-of-concept experiments are carried out. The basic waveforms, including Gaussian, saw-up, and saw-down waveforms, with full duty and small duty cycle are generated at the repetition rate of 2 GHz. The theoretical and simulation results agree with the experimental results very well.

Pronunciation difficulty, temporal regularity, and the speech-to-song illusion.

PubMed

Margulis, Elizabeth H; Simchy-Gross, Rhimmon; Black, Justin L

2015-01-01

The speech-to-song illusion (Deutsch et al., 2011) tracks the perceptual transformation from speech to song across repetitions of a brief spoken utterance. Because it involves no change in the stimulus itself, but a dramatic change in its perceived affiliation to speech or to music, it presents a unique opportunity to comparatively investigate the processing of language and music. In this study, native English-speaking participants were presented with brief spoken utterances that were subsequently repeated ten times. The utterances were drawn either from languages that are relatively difficult for a native English speaker to pronounce, or languages that are relatively easy for a native English speaker to pronounce. Moreover, the repetition could occur at regular or irregular temporal intervals. Participants rated the utterances before and after the repetitions on a 5-point Likert-like scale ranging from "sounds exactly like speech" to "sounds exactly like singing." The difference in ratings before and after was taken as a measure of the strength of the speech-to-song illusion in each case. The speech-to-song illusion occurred regardless of whether the repetitions were spaced at regular temporal intervals or not; however, it occurred more readily if the utterance was spoken in a language difficult for a native English speaker to pronounce. Speech circuitry seemed more liable to capture native and easy-to-pronounce languages, and more reluctant to relinquish them to perceived song across repetitions.

Variability, constraints, and creativity. Shedding light on Claude Monet.

PubMed

Stokes, P D

2001-04-01

Recent experimental research suggests 2 things. The first is that along with learning how to do something, people also learn how variably or differently to continue doing it. The second is that high variability is maintained by constraining, precluding a currently successful, often repetitive solution to a problem. In this view, Claude Monet's habitually high level of variability in painting was acquired during his childhood and early apprenticeship and was maintained throughout his adult career by a continuous series of task constraints imposed by the artist on his own work. For Monet, variability was rewarded and rewarding.

Repetitive nanosecond electron accelerators type URT-1 for radiation technology

NASA Astrophysics Data System (ADS)

Sokovnin, S. Yu.; Balezin, M. E.

2018-03-01

The electron accelerator URT-1М-300 for mobile installation was created for radiation disinfecting to correct drawbacks that were found the URT-1M electron accelerator operation (the accelerating voltage up to 1 МV, repetition rate up to 300 pps, electron beam size 400 × 100 mm, the pulse width about 100 ns). Accelerator configuration was changed that allowed to reduce significantly by 20% tank volume with oil where is placed the system of formation high-voltage pulses, thus the average power of the accelerator is increased by 6 times at the expense of increase in pulses repetition rate. Was created the system of the computerized monitoring parameters (output parameters and thermal mode) and remote control of the accelerator (charge voltage, pulse repetition rate), its elements and auxiliary systems (heat of the thyratron, vacuum system), the remote control panel is connected to the installation by the fiber-optical channel, what lightens the work for service personnel. For generating an electron beam up to 400 mm wide there are used metal- ceramic] and metal-dielectric cold cathodes of several emission elements (plates) with a non-uniform distribution of the electron beam current density on the output foil ± 15%. It was found that emission drop of both type of cathodes, during the operation at the high repetition rate (100 pps) is substantial at the beginning of the process, and then proceeds rather slowly that allows for continuous operation up to 40 h. Experiments showed that linear dependence of the voltage and a signal from the pin-diode remains within the range of the charge voltage 45-65 kV. Thus, voltage increases from 690 to 950 kV, and the signal from the pin-diode - from (2,8-4,6)*104 Gy/s. It allows to select electron energy quite precisely with consideration of the radiation technology requirements.

Scaling of echolocation call parameters in bats.

PubMed

Jones, G

1999-12-01

I investigated the scaling of echolocation call parameters (frequency, duration and repetition rate) in bats in a functional context. Low-duty-cycle bats operate with search phase cycles of usually less than 20 %. They process echoes in the time domain and are therefore intolerant of pulse-echo overlap. High-duty-cycle (>30 %) species use Doppler shift compensation, and they separate pulse and echo in the frequency domain. Call frequency scales negatively with body mass in at least five bat families. Pulse duration scales positively with mass in low-duty-cycle quasi-constant-frequency (QCF) species because the large aerial-hawking species that emit these signals fly fast in open habitats. They therefore detect distant targets and experience pulse-echo overlap later than do smaller bats. Pulse duration also scales positively with mass in the Hipposideridae, which show at least partial Doppler shift compensation. Pulse repetition rate corresponds closely with wingbeat frequency in QCF bat species that fly relatively slowly. Larger, fast-flying species often skip pulses when detecting distant targets. There is probably a trade-off between call intensity and repetition rate because 'whispering' bats (and hipposiderids) produce several calls per predicted wingbeat and because batches of calls are emitted per wingbeat during terminal buzzes. Severe atmospheric attenuation at high frequencies limits the range of high-frequency calls. Low-duty-cycle bats that call at high frequencies must therefore use short pulses to avoid pulse-echo overlap. Rhinolophids escape this constraint by Doppler shift compensation and, importantly, can exploit advantages associated with the emission of both high-frequency and long-duration calls. Low frequencies are unsuited for the detection of small prey, and low repetition rates may limit prey detection rates. Echolocation parameters may therefore constrain maximum body size in aerial-hawking bats.

Ultrafast high-repetition imaging of fuel sprays using picosecond fiber laser.

PubMed

Purwar, Harsh; Wang, Hongjie; Tang, Mincheng; Idlahcen, Saïd; Rozé, Claude; Blaisot, Jean-Bernard; Godin, Thomas; Hideur, Ammar

2015-12-28

Modern diesel injectors operate at very high injection pressures of about 2000 bar resulting in injection velocities as high as 700 m/s near the nozzle outlet. In order to better predict the behavior of the atomization process at such high pressures, high-resolution spray images at high repetition rates must be recorded. However, due to extremely high velocity in the near-nozzle region, high-speed cameras fail to avoid blurring of the structures in the spray images due to their exposure time. Ultrafast imaging featuring ultra-short laser pulses to freeze the motion of the spray appears as an well suited solution to overcome this limitation. However, most commercial high-energy ultrafast sources are limited to a few kHz repetition rates. In the present work, we report the development of a custom-designed picosecond fiber laser generating ∼ 20 ps pulses with an average power of 2.5 W at a repetition rate of 8.2 MHz, suitable for high-speed imaging of high-pressure fuel jets. This fiber source has been proof tested by obtaining backlight images of diesel sprays issued from a single-orifice injector at an injection pressure of 300 bar. We observed a consequent improvement in terms of image resolution compared to standard white-light illumination. In addition, the compactness and stability against perturbations of our fiber laser system makes it particularly suitable for harsh experimental conditions.

High-pulse-energy mode-locked picosecond oscillator

NASA Astrophysics Data System (ADS)

Chao, Yang; Chen, Meng; Li, Gang

2014-02-01

We report on a high-pulse-energy solid-state picosecond Nd:YVO4 oscillator with cavity-dumping. The laser is end-pumped by an 808 nm laser diode and passively mode-locked with a semiconductor saturable absorption mirror (SESAM). In pure cw-mode-locking, this laser produced 2.5 W of average power at a pulse repetition rate of 40 MHz and pulse duration around 12 ps. A cavity dumping technique using an intra-cavity BBO electro-optic crystal to which bidirectional voltage was applied was adopted, effectively improving the cavity-dumping rate. Tunable high repetition rate from 100 kHz to 1 MHz was achieved. With electro-optic cavity dumper working at 1 MHz repetition rate, we achieved average power 594 mW. The laser includes a 5 mm long, a-cut, 0.5% doped Nd:YVO4 crystal with a 5-degree angle at one end face. Laser radiation is coupled out from the crystal end face with a 5-degree angle, without requiring insertion of a thin-film polarizer (TFP), thus simplifying the laser structure. This picosecond laser system has the advantages of compact structure and high stability, providing a good oscillator for regenerative amplifiers.

20 kHz toluene planar laser-induced fluorescence imaging of a jet in nearly sonic crossflow

NASA Astrophysics Data System (ADS)

Miller, V. A.; Troutman, V. A.; Mungal, M. G.; Hanson, R. K.

2014-10-01

This manuscript describes continuous, high-repetition-rate (20 kHz) toluene planar laser-induced fluorescence (PLIF) imaging in an expansion tube impulse flow facility. Cinematographic image sequences are acquired that visualize an underexpanded jet of hydrogen in Mach 0.9 crossflow, a practical flow configuration relevant to aerospace propulsion systems. The freestream gas is nitrogen seeded with toluene; toluene broadly absorbs and fluoresces in the ultraviolet, and the relatively high quantum yield of toluene produces large signals and high signal-to-noise ratios. Toluene is excited using a commercially available, frequency-quadrupled (266 nm), high-repetition-rate (20 kHz), pulsed (0.8-0.9 mJ per pulse), diode-pumped solid-state Nd:YAG laser, and fluorescence is imaged with a high-repetition-rate intensifier and CMOS camera. The resulting PLIF movie and image sequences are presented, visualizing the jet start-up process and the dynamics of the jet in crossflow; the freestream duration and a measure of freestream momentum flux steadiness are also inferred. This work demonstrates progress toward continuous PLIF imaging of practical flow systems in impulse facilities at kHz acquisition rates using practical, turn-key, high-speed laser and imaging systems.

Secrets of virtuoso: neuromuscular attributes of motor virtuosity in expert musicians

PubMed Central

Furuya, Shinichi; Oku, Takanori; Miyazaki, Fumio; Kinoshita, Hiroshi

2015-01-01

Musical performance requires extremely fast and dexterous limb movements. The underlying biological mechanisms have been an object of interest among scientists and non-scientists for centuries. Numerous studies of musicians and non-musicians have demonstrated that neuroplastic adaptations through early and deliberate musical training endowed superior motor skill. However, little has been unveiled about what makes inter-individual differences in motor skills among musicians. Here we determined the attributes of inter-individual differences in the maximum rate of repetitive piano keystrokes in twenty-four pianists. Among various representative factors of neuromuscular functions, anatomical characteristics, and training history, a stepwise multiple regression analysis and generalized linear model identified two predominant predictors of the maximum rate of repetitive piano keystrokes; finger tapping rate and muscular strength of the elbow extensor. These results suggest a non-uniform role of individual limb muscles in the production of extremely fast repetitive multi-joint movements. Neither age of musical training initiation nor the amount of extensive musical training before age twenty was a predictor. Power grip strength was negatively related to the maximum rate of piano keystrokes only during the smallest tone production. These findings highlight the importance of innate biological nature and explicit training for motor virtuosity. PMID:26502770

The Repeat Sequences and Elevated Substitution Rates of the Chloroplast accD Gene in Cupressophytes

PubMed Central

Li, Jia; Su, Yingjuan; Wang, Ting

2018-01-01

The plastid accD gene encodes a subunit of the acetyl-CoA carboxylase (ACCase) enzyme. The length of accD gene has been supposed to expand in Cryptomeria japonica, Taiwania cryptomerioides, Cephalotaxus, Taxus chinensis, and Podocarpus lambertii, and the main reason for this phenomenon was the existence of tandemly repeated sequences. However, it is still unknown whether the accD gene length in other cupressophytes has expanded. Here, in order to investigate how widespread this phenomenon was, 18 accD sequences and its surrounding regions of cupressophyte were sequenced and analyzed. Together with 39 GenBank sequence data, our taxon sampling covered all the extant gymnosperm orders. The repetitive elements and substitution rates of accD among 57 gymnosperm species were analyzed, the results show: (1) Reading frame length of accD gene in 18 cupressophytes species has also expanded. (2) Many repetitive elements were identified in accD gene of cupressophyte lineages. (3) The synonymous and non-synonymous substitution rates of accD were accelerated in cupressophytes. (4) accD was located in rearrangement endpoints. These results suggested that repetitive elements may mediate the chloroplast genome rearrangement and accelerated the substitution rates. PMID:29731764

Secrets of virtuoso: neuromuscular attributes of motor virtuosity in expert musicians

NASA Astrophysics Data System (ADS)

Furuya, Shinichi; Oku, Takanori; Miyazaki, Fumio; Kinoshita, Hiroshi

2015-10-01

Musical performance requires extremely fast and dexterous limb movements. The underlying biological mechanisms have been an object of interest among scientists and non-scientists for centuries. Numerous studies of musicians and non-musicians have demonstrated that neuroplastic adaptations through early and deliberate musical training endowed superior motor skill. However, little has been unveiled about what makes inter-individual differences in motor skills among musicians. Here we determined the attributes of inter-individual differences in the maximum rate of repetitive piano keystrokes in twenty-four pianists. Among various representative factors of neuromuscular functions, anatomical characteristics, and training history, a stepwise multiple regression analysis and generalized linear model identified two predominant predictors of the maximum rate of repetitive piano keystrokes; finger tapping rate and muscular strength of the elbow extensor. These results suggest a non-uniform role of individual limb muscles in the production of extremely fast repetitive multi-joint movements. Neither age of musical training initiation nor the amount of extensive musical training before age twenty was a predictor. Power grip strength was negatively related to the maximum rate of piano keystrokes only during the smallest tone production. These findings highlight the importance of innate biological nature and explicit training for motor virtuosity.

DC-driven plasma gun: self-oscillatory operation mode of atmospheric-pressure helium plasma jet comprised of repetitive streamer breakdowns

NASA Astrophysics Data System (ADS)

Wang, Xingxing; Shashurin, Alexey

2017-02-01

This paper presents and studies helium atmospheric pressure plasma jet comprised of a series of repetitive streamer breakdowns, which is driven by pure DC high voltage (self-oscillatory behavior). The repetition frequency of the breakdowns is governed by the geometry of discharge electrodes/surroundings and gas flow rate. Each next streamer is initiated when the electric field on the anode tip recovers after the previous breakdown and reaches the breakdown threshold value of about 2.5 kV cm-1. One type of the helium plasma gun designed using this operational principle is demonstrated. The gun operates on about 3 kV DC high voltage and is comprised of the series of the repetitive streamer breakdowns at a frequency of about 13 kHz.

Note: Repetitive operation of the capacitor bank of the low-voltage miniature plasma focus at 50 Hz.

PubMed

Shukla, Rohit; Shyam, Anurag

2013-10-01

We have already reported the low-voltage operation of a plasma focus describing the operation of plasma focus at 4.2 kV which proposes possibility of making a repetitive system using compact driving source. Another recent article describes that the same capacitor-bank can drive the plasma focus for a measured ~5 × 10(4) neutrons per shot at 5 kV and 59 kA current. In the present work, repetitive operation of the capacitor-bank of plasma focus is done and that too is being reported at a very high repetition rate of 50 Hz using very simple scheme of charging and triggering the bank. The bank is continuously discharged to burst duration of 20 s in this configuration admeasuring a thousand shots.

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.

Dual-comb coherent Raman spectroscopy with lasers of 1-GHz pulse repetition frequency.

PubMed

Mohler, Kathrin J; Bohn, Bernhard J; Yan, Ming; Mélen, Gwénaëlle; Hänsch, Theodor W; Picqué, Nathalie

2017-01-15

We extend the technique of multiplex coherent Raman spectroscopy with two femtosecond mode-locked lasers to oscillators of a pulse repetition frequency of 1 GHz. We demonstrate a spectra of liquids, which span 1100  cm^-1 of Raman shifts. At a resolution of 6  cm^-1, their measurement time may be as short as 5 μs for a refresh rate of 2 kHz. The waiting period between acquisitions is improved 10-fold compared to previous experiments with two lasers of 100-MHz repetition frequencies.

Application of microplasma discharge in a spark gap for high repetitive switching

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

Rahaman, Hasibur; Nam, Sang Hoon; Nam, Jong Woo

2010-04-05

The electrical breakdown in a spark gap for repetitive switching has been a long research interest. For this purpose, microplasma discharge is implemented in the spark gap which is further integrated inside a coaxial transmission line. This work addresses important physical properties and insights of the microplasma discharge, to be optimized, such as plasma generation in a spark channel, dielectric recovery process, and residual plasma in the postspark discharge period. Although understanding the microplasma discharge is the primary goal, considerable attention has been focused on an external circuit scheme to drive the discharge system at a high repetition rate.

Effect of a 10-week strength training program and recovery drink on body composition, muscular strength and endurance, and anaerobic power and capacity.

PubMed

Chromiak, Joseph A; Smedley, Brianne; Carpenter, William; Brown, Robert; Koh, Yun S; Lamberth, John G; Joe, Lee Ann; Abadie, Ben R; Altorfer, Greg

2004-05-01

We investigated whether postexercise consumption of a supplement containing whey protein, amino acids, creatine, and carbohydrate combined with a strength training program promotes greater gains in fat-free mass (FFM), muscle strength and endurance, and anaerobic performance compared with an isocaloric, carbohydrate-only control drink combined with strength training. The study was double blind and randomized, and the experimental supplement was compared with a carbohydrate-only control. Forty-one males (n = 20 in control group, n = 21 in the supplement group; mean age, 22.2 y) participated in a 4 d/wk, 10-wk periodized strength training program. Subjects had to complete at least 70% of the workouts. Before and after 10 wk of strength training, subjects were tested for body composition by using hydrostatic weighing and skinfold thicknesses, one repetition maximum strength and muscular endurance for the bench press and 45-degree leg press, and anaerobic performance using a 30-s Wingate test. Thirty-three subjects (80.5%) completed the training program (n = 15 in control group, n = 18 in the supplement); these 33 subjects also completed all post-training test procedures. Data were analyzed with two-way analysis of variance with repeated measures on time. P <== 0.05 was set as statistically significant. All statistical analyses, including calculation of effect size and power, were completed with SPSS 11.0. Across groups, FFM increased during 10 wk of strength training. Although there was no statistically significant time x group interaction for FFM, there was a trend toward a greater increase in FFM for the supplement group (+3.4 kg) compared with the control group (+1.5 kg; P = 0.077). The effect size (eta(2) = 0.100) was moderately large. Percentage of body fat declined and fat mass was unchanged; there were no differences between groups. One repetition maximum strength for the bench press and 45-degree leg press increased, but there were no differences between groups. Muscular endurance expressed as the number of repetitions completed with 85% of the one repetition maximum was unchanged; external work, which was estimated as repetitions completed x resistance used, increased for the 45-degree leg press but not for the bench press over the 10-wk training period; there were no time x group interactions for either measurement. Anaerobic power and capacity improved, but there were no differences between groups for these variables or for fatigue rate. Consumption of a recovery drink after strength training workouts did not promote greater gains in FFM compared with consumption of a carbohydrate-only drink; however, a trend toward a greater increase in FFM in the supplement group suggests the need for longer-term studies. Performance variables such as muscle strength and endurance and anaerobic performance were not improved when compared with the carbohydrate-only group.

Probing ultra-fast processes with high dynamic range at 4th-generation light sources: Arrival time and intensity binning at unprecedented repetition rates.

PubMed

Kovalev, S; Green, B; Golz, T; Maehrlein, S; Stojanovic, N; Fisher, A S; Kampfrath, T; Gensch, M

2017-03-01

Understanding dynamics on ultrafast timescales enables unique and new insights into important processes in the materials and life sciences. In this respect, the fundamental pump-probe approach based on ultra-short photon pulses aims at the creation of stroboscopic movies. Performing such experiments at one of the many recently established accelerator-based 4th-generation light sources such as free-electron lasers or superradiant THz sources allows an enormous widening of the accessible parameter space for the excitation and/or probing light pulses. Compared to table-top devices, critical issues of this type of experiment are fluctuations of the timing between the accelerator and external laser systems and intensity instabilities of the accelerator-based photon sources. Existing solutions have so far been only demonstrated at low repetition rates and/or achieved a limited dynamic range in comparison to table-top experiments, while the 4th generation of accelerator-based light sources is based on superconducting radio-frequency technology, which enables operation at MHz or even GHz repetition rates. In this article, we present the successful demonstration of ultra-fast accelerator-laser pump-probe experiments performed at an unprecedentedly high repetition rate in the few-hundred-kHz regime and with a currently achievable optimal time resolution of 13 fs (rms). Our scheme, based on the pulse-resolved detection of multiple beam parameters relevant for the experiment, allows us to achieve an excellent sensitivity in real-world ultra-fast experiments, as demonstrated for the example of THz-field-driven coherent spin precession.

On the Dissociation of Word/Nonword Repetition Effects in Lexical Decision: An Evidence Accumulation Account.

PubMed

Perea, Manuel; Marcet, Ana; Vergara-Martínez, Marta; Gomez, Pablo

2016-01-01

A number of models of visual-word recognition assume that the repetition of an item in a lexical decision experiment increases that item's familiarity/wordness. This would produce not only a facilitative repetition effect for words, but also an inhibitory effect for nonwords (i.e., more familiarity/wordness makes the negative decision slower). We conducted a two-block lexical decision experiment to examine word/nonword repetition effects in the framework of a leading "familiarity/wordness" model of the lexical decision task, namely, the diffusion model (Ratcliff et al., 2004). Results showed that while repeated words were responded to faster than the unrepeated words, repeated nonwords were responded to more slowly than the nonrepeated nonwords. Fits from the diffusion model revealed that the repetition effect for words/nonwords was mainly due to differences in the familiarity/wordness (drift rate) parameter. This word/nonword dissociation favors those accounts that posit that the previous presentation of an item increases its degree of familiarity/wordness.

On the Dissociation of Word/Nonword Repetition Effects in Lexical Decision: An Evidence Accumulation Account

PubMed Central

Perea, Manuel; Marcet, Ana; Vergara-Martínez, Marta; Gomez, Pablo

2016-01-01

A number of models of visual-word recognition assume that the repetition of an item in a lexical decision experiment increases that item's familiarity/wordness. This would produce not only a facilitative repetition effect for words, but also an inhibitory effect for nonwords (i.e., more familiarity/wordness makes the negative decision slower). We conducted a two-block lexical decision experiment to examine word/nonword repetition effects in the framework of a leading “familiarity/wordness” model of the lexical decision task, namely, the diffusion model (Ratcliff et al., 2004). Results showed that while repeated words were responded to faster than the unrepeated words, repeated nonwords were responded to more slowly than the nonrepeated nonwords. Fits from the diffusion model revealed that the repetition effect for words/nonwords was mainly due to differences in the familiarity/wordness (drift rate) parameter. This word/nonword dissociation favors those accounts that posit that the previous presentation of an item increases its degree of familiarity/wordness. PMID:26925021

Oral-Diadochokinetic Rates for Hebrew-Speaking Healthy Ageing Population: Non-Word versus Real-Word Repetition

ERIC Educational Resources Information Center

Ben-David, Boaz M.; Icht, Michal

2017-01-01

Background: Oral-diadochokinesis (oral-DDK) tasks are extensively used in the evaluation of motor speech abilities. Currently, validated normative data for older adults (aged 65 years and older) are missing in Hebrew. The effect of task stimuli (non-word versus real-word repetition) is also non-clear in the population of older adult Hebrew…

Influence of speech sample on perceptual rating of hypernasality.

PubMed

Medeiros, Maria Natália Leite de; Fukushiro, Ana Paula; Yamashita, Renata Paciello

2016-07-07

To investigate the influence of speech sample of spontaneous conversation or sentences repetition on intra and inter-rater hypernasality reliability. One hundred and twenty audio recorded speech samples (60 containing spontaneous conversation and 60 containing repeated sentences) of individuals with repaired cleft palate±lip, both genders, aged between 6 and 52 years old (mean=21±10) were selected and edited. Three experienced speech and language pathologists rated hypernasality according to their own criteria using 4-point scale: 1=absence of hypernasality, 2=mild hypernasality, 3=moderate hypernasality and 4=severe hypernasality, first in spontaneous speech samples and 30 days after, in sentences repetition samples. Intra- and inter-rater agreements were calculated for both speech samples and were statistically compared by the Z test at a significance level of 5%. Comparison of intra-rater agreements between both speech samples showed an increase of the coefficients obtained in the analysis of sentences repetition compared to those obtained in spontaneous conversation. Comparison between inter-rater agreement showed no significant difference among the three raters for the two speech samples. Sentences repetition improved intra-raters reliability of perceptual judgment of hypernasality. However, the speech sample had no influence on reliability among different raters.

Reversing-counterpulse repetitive-pulse inductive storage circuit

DOEpatents

Honig, E.M.

1987-02-10

A high-power reversing-counterpulse repetitive-pulse inductive storage and transfer circuit includes an opening switch, a main energy storage coil, a counterpulse capacitor and a small inductor. After counterpulsing the opening switch off, the counterpulse capacitor is recharged by the main energy storage coil before the load pulse is initiated. This gives the counterpulse capacitor sufficient energy for the next counterpulse operation, although the polarity of the capacitor's voltage must be reversed before that can occur. By using a current-zero switch as the counterpulse start switch, the capacitor is disconnected from the circuit (with a full charge) when the load pulse is initiated, preventing the capacitor from depleting its energy store by discharging through the load. After the load pulse is terminated by reclosing the main opening switch, the polarity of the counterpulse capacitor voltage is reversed by discharging the capacitor through a small inductor and interrupting the discharge current oscillation at zero current and peak reversed voltage. The circuit enables high-power, high-repetition-rate operation with reusable switches and features total control (pulse-to-pulse) over output pulse initiation, duration, repetition rate, and, to some extent, risetime. 10 figs.

Beauty is in the belief of the beholder: cognitive influences on the neural response to facial attractiveness

PubMed Central

Thiruchselvam, Ravi; Harper, Jessica; Homer, Abigail L.

2016-01-01

Judgments of facial attractiveness are central to decision-making in various domains, but little is known about the extent to which they are malleable. In this study, we used EEG/ERP methods to examine two novel influences on neural and subjective responses to facial attractiveness: an observer’s expectation and repetition. In each trial of our task, participants viewed either an ordinary or attractive face. To alter expectations, the faces were preceded by a peer-rating that ostensibly reflected the overall attractiveness value assigned to that face by other individuals. To examine the impact of repetition, trials were presented twice throughout the experimental session. Results showed that participants’ expectations about a person’s attractiveness level powerfully altered both the neural response (i.e. the late positive potential; LPP) and self-reported attractiveness ratings. Intriguingly, repetition enhanced both the LPP and self-reported attractiveness as well. Exploratory analyses further suggested that both observer expectation and repetition modulated early neural responses (i.e. the early posterior negativity; EPN) elicited by facial attractiveness. Collectively, these results highlight novel influences on a core social judgment that underlies individuals’ affective lives. PMID:27522090

Individual aptitude in Mandarin lexical tone perception predicts effectiveness of high-variability training

PubMed Central

Sadakata, Makiko; McQueen, James M.

2014-01-01

Although the high-variability training method can enhance learning of non-native speech categories, this can depend on individuals’ aptitude. The current study asked how general the effects of perceptual aptitude are by testing whether they occur with training materials spoken by native speakers and whether they depend on the nature of the to-be-learned material. Forty-five native Dutch listeners took part in a 5-day training procedure in which they identified bisyllabic Mandarin pseudowords (e.g., asa) pronounced with different lexical tone combinations. The training materials were presented to different groups of listeners at three levels of variability: low (many repetitions of a limited set of words recorded by a single speaker), medium (fewer repetitions of a more variable set of words recorded by three speakers), and high (similar to medium but with five speakers). Overall, variability did not influence learning performance, but this was due to an interaction with individuals’ perceptual aptitude: increasing variability hindered improvements in performance for low-aptitude perceivers while it helped improvements in performance for high-aptitude perceivers. These results show that the previously observed interaction between individuals’ aptitude and effects of degree of variability extends to natural tokens of Mandarin speech. This interaction was not found, however, in a closely matched study in which native Dutch listeners were trained on the Japanese geminate/singleton consonant contrast. This may indicate that the effectiveness of high-variability training depends not only on individuals’ aptitude in speech perception but also on the nature of the categories being acquired. PMID:25505434

Global Sea-level Changes Revealed in the Sediments of the Canterbury Basin, New Zealand: IODP Expedition 317

NASA Astrophysics Data System (ADS)

McHugh, C. M.; Fulthorpe, C.; Blum, P.; Rios, J.; Chow, Y.; Mishkin, K.

2012-12-01

Continental margins are composed of thick sedimentary sections that preserve the record of local processes modulated by global sea-level (eustatic) changes and climate. Understanding this regional variability permits us to extract the eustatic record. Integrated Ocean Drilling Program Expedition 317 drilled four sites in the offshore Canterbury Basin, eastern South Island of New Zealand, in water depths of 85 m to 320 m. One of the objectives of the expedition was to understand the influence of eustasy on continental margins sedimentation and to test the concepts of sequence stratigraphy. A high-resolution multiproxy approach that involves geochemical elemental analyses, lithostratigraphy and biostratigraphy is applied to understand the margin's sedimentation for the past ~5 million years. Multichannel seismic data (EW00-01 survey) provide a seismic sequence stratigraphic framework against which to interpret the multiproxy data. The mid- to late Pleistocene sedimentation is characterized by variable lithologies and changing facies. However, elemental compositions and facies follow predictable patterns within seismic sequences. Oxygen isotope measurements for the latest Pleistocene indicate that 100 ky Milankovich astronomical forcing controlled this variability. In contrast, Pliocene and early Pleistocene sediments are composed of repetitive siliciclastic and carbonate mud lithologies with less facies variability. Results of our analyses suggest that repetitive alternations of green and gray mud were deposited during warmer and cooler periods, respectively. Oxygen isotopes suggest that this cyclicity may reflect 40 ky Milankovich forcing. Ocean Drilling Program Legs 150 and 174A drilled on the New Jersey continental margin with similar objectives to those of Expedition 317. Results from this northern and southern hemisphere drilling reveal that eustasy, controlled by Milankovich forcing, strongly influences margin sedimentation and the formation of basin-wide unconformities. However, the correlation between eustasy and seismic sequence formation is not always one to one. High sedimentation rates in the Pleistocene offshore Canterbury Basin record a one- to-one correlation between glacioeustasy and seismic sequences, and in some sequences possibly a higher order frequency. But this is not the case for offshore New Jersey, where accumulation rates were lower and only the uppermost seismic sequences represent 100 ky cycles. Furthermore, Pliocene sedimentation in the Canterbury Basin was also controlled by eustasy, but does not show a one-to-one correlation between Milankovich cycles and seismic stratigraphy. Northern and southern hemisphere comparisons provide a powerful tool to better understand controls on regional sedimentation and extract a global signal.

Vector similariton erbium-doped all-fiber laser generating sub-100-fs nJ pulses at 100 MHz.

PubMed

Olivier, Michel; Piché, Michel

2016-02-08

Erbium-doped mode-locked fiber lasers with repetition rates comparable to those of solid-state lasers and generating nJ pulses are required for many applications. Our goal was to design a fiber laser that would meet such requirements, that could be built at relatively low cost and that would be reliable and robust. We thus developed a high-fundamental-repetition-rate erbium-doped all-fiber laser operating in the amplifier similariton regime. Experimental characterization shows that this laser, which is mode-locked by nonlinear polarization evolution, emits 76-fs pulses with an energy of 1.17 nJ at a repetition rate of 100 MHz. Numerical simulations support the interpretation of self-similar evolution of the pulse in the gain fiber. More specifically we introduce the concept of vector similariton in fiber lasers. The coupled x- and y- polarization components of such a pulse have a pulse profile with a linear chirp and their combined power profile evolves self-similarly when the nonlinear asymptotic regime is reached in the gain fiber.

Gain-switched laser diode seeded Yb-doped fiber amplifier delivering 11-ps pulses at repetition rates up to 40-MHz

NASA Astrophysics Data System (ADS)

Ryser, Manuel; Neff, Martin; Pilz, Soenke; Burn, Andreas; Romano, Valerio

2012-02-01

Here, we demonstrate all-fiber direct amplification of 11 picosecond pulses from a gain-switched laser diode at 1063 nm. The diode was driven at a repetition rate of 40 MHz and delivered 13 μW of fiber-coupled average output power. For the low output pulse energy of 0.33 pJ we have designed a multi-stage core pumped preamplifier based on single clad Yb-doped fibers in order to keep the contribution of undesired amplified spontaneous emission as low as possible and to minimize temporal and spectral broadening. After the preamplifier we reduced the 40 MHz repetition rate to 1 MHz using a fiber coupled pulse-picker. The final amplification was done with a cladding pumped Yb-doped large mode area fiber and a subsequent Yb-doped rod-type fiber. With our setup we achieved amplification of 72 dBs to an output pulse energy of 5.7 μJ, pulse duration of 11 ps and peak power of >0.6 MW.

Monolithic all-fiber repetition-rate tunable gain-switched single-frequency Yb-doped fiber laser.

PubMed

Hou, Yubin; Zhang, Qian; Qi, Shuxian; Feng, Xian; Wang, Pu

2016-12-12

We report a monolithic gain-switched single-frequency Yb-doped fiber laser with widely tunable repetition rate. The single-frequency laser operation is realized by using an Yb-doped distributed Bragg reflection (DBR) fiber cavity, which is pumped by a commercial-available laser diode (LD) at 974 nm. The LD is electronically modulated by the driving current and the diode output contains both continuous wave (CW) and pulsed components. The CW component is set just below the threshold of the single-frequency fiber laser for reducing the requirement of the pump pulse energy. Above the threshold, the gain-switched oscillation is trigged by the pulsed component of the diode. Single-frequency pulsed laser output is achieved at 1.063 μm with a pulse duration of ~150 ns and a linewidth of 14 MHz. The repetition rate of the laser output can be tuned between 10 kHz and 400 kHz by tuning the electronic trigger signal. This kind of lasers shows potential for the applications in the area of coherent LIDAR etc.

Bright high-repetition-rate source of narrowband extreme-ultraviolet harmonics beyond 22 eV

PubMed Central

Wang, He; Xu, Yiming; Ulonska, Stefan; Robinson, Joseph S.; Ranitovic, Predrag; Kaindl, Robert A.

2015-01-01

Novel table-top sources of extreme-ultraviolet light based on high-harmonic generation yield unique insight into the fundamental properties of molecules, nanomaterials or correlated solids, and enable advanced applications in imaging or metrology. Extending high-harmonic generation to high repetition rates portends great experimental benefits, yet efficient extreme-ultraviolet conversion of correspondingly weak driving pulses is challenging. Here, we demonstrate a highly-efficient source of femtosecond extreme-ultraviolet pulses at 50-kHz repetition rate, utilizing the ultraviolet second-harmonic focused tightly into Kr gas. In this cascaded scheme, a photon flux beyond ≈3 × 1013 s−1 is generated at 22.3 eV, with 5 × 10−5 conversion efficiency that surpasses similar harmonics directly driven by the fundamental by two orders-of-magnitude. The enhancement arises from both wavelength scaling of the atomic dipole and improved spatio-temporal phase matching, confirmed by simulations. Spectral isolation of a single 72-meV-wide harmonic renders this bright, 50-kHz extreme-ultraviolet source a powerful tool for ultrafast photoemission, nanoscale imaging and other applications. PMID:26067922

kW picosecond thin-disk regenerative amplifier

NASA Astrophysics Data System (ADS)

Michel, Knut; Wandt, Christoph; Klingebiel, Sandro; Schultze, Marcel; Prinz, Stephan; Teisset, Catherine Y.; Stark, Sebastian; Grebing, Christian; Bessing, Robert; Herzig, Tobias; Häfner, Matthias; Budnicki, Aleksander; Sutter, Dirk; Metzger, Thomas

2018-02-01

TRUMPF Scientific Lasers provides ultrafast laser sources for the scientific community with high pulse energies and high average power. All systems are based on the industrialized TRUMPF thin-disk technology. Regenerative amplifiers systems with multi-millijoule pulses, kilohertz repetition rates and picosecond pulse durations are available. Record values of 220mJ at 1kHz could be demonstrated originally developed for pumping optical parametric amplifiers. The ultimate goal is to combine high energies, <100mJ per pulse, with average powers of several hundred watts to a kilowatt. Based on a regenerative amplifier containing two Ytterbium doped thin-disks operated at ambient temperature pulses with picosecond duration and more than 100mJ could be generated at a repetition rate of 10kHz reaching 1kW of average output power. This system is designed to operate at different repetition rates from 100kHz down to 5kHz so that even higher pulse energies can be reached. This type of ultrafast sources uncover new application fields in science. Laser based lightning rods, X-ray lasers and Compton backscatter sources are among them.

Repetition rate multiplication of frequency comb using all-pass fiber resonator

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

Yang, Lijun; Yang, Honglei; Zhang, Hongyuan

2016-09-15

We propose a stable method for repetition rate multiplication of a 250-MHz Er-fiber frequency comb by a phase-locked all-pass fiber ring resonator, whose phase-locking configuration is simple. The optical path length of the fiber ring resonator is automatically controlled to be accurately an odd multiple of half of the original cavity length using an electronical phase-locking unit with an optical delay line. As for shorter cavity length of the comb, high-order odd multiple is preferable. Because the power loss depends only on the net-attenuation of the fiber ring resonator, the energetic efficiency of the proposed method is high. The inputmore » and output optical spectrums show that the spectral width of the frequency comb is clearly preserved. Besides, experimental results show less pulse intensity fluctuation and 35 dB suppression ratio of side-modes while providing a good long-term and short-term frequency stability. Higher-order repetition rate multiplication to several GHz can be obtained by using several fiber ring resonators in cascade configuration.« less

High-power, highly stable KrF laser with a 4-kHz pulse repetition rate

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

Borisov, V M; El'tsov, A V; Khristoforov, O B

2015-08-31

An electric-discharge KrF laser (248 nm) with an average output power of 300 W is developed and studied. A number of new design features are related to the use of a laser chamber based on an Al{sub 2}O{sub 3} ceramic tube. A high power and pulse repetition rate are achieved by using a volume discharge with lateral preionisation by the UV radiation of a creeping discharge in the form of a homogeneous plasma sheet on the surface of a plane sapphire plate. Various generators for pumping the laser are studied. The maximum laser efficiency is 3.1%, the maximum laser energymore » is 160 mJ pulse{sup -1}, and the pulse duration at half maximum is 7.5 ns. In the case of long-term operation at a pulse repetition rate of 4 kHz and an output power of 300 W, high stability of laser output energy (σ ≤ 0.7%) is achieved using an all-solid-state pump system. (lasers)« less

Learning curves and impact of previous operative experience on performance on a virtual reality simulator to test laparoscopic surgical skills.

PubMed

Grantcharov, Teodor P; Bardram, Linda; Funch-Jensen, Peter; Rosenberg, Jacob

2003-02-01

The study was carried out to analyze the learning rate for laparoscopic skills on a virtual reality training system and to establish whether the simulator was able to differentiate between surgeons with different laparoscopic experience. Forty-one surgeons were divided into three groups according to their experience in laparoscopic surgery: masters (group 1, performed more than 100 cholecystectomies), intermediates (group 2, between 15 and 80 cholecystectomies), and beginners (group 3, fewer than 10 cholecystectomies) were included in the study. The participants were tested on the Minimally Invasive Surgical Trainer-Virtual Reality (MIST-VR) 10 consecutive times within a 1-month period. Assessment of laparoscopic skills included time, errors, and economy of hand movement, measured by the simulator. The learning curves regarding time reached plateau after the second repetition for group 1, the fifth repetition for group 2, and the seventh repetition for group 3 (Friedman's tests P <0.05). Experienced surgeons did not improve their error or economy of movement scores (Friedman's tests, P >0.2) indicating the absence of a learning curve for these parameters. Group 2 error scores reached plateau after the first repetition, and group 3 after the fifth repetition. Group 2 improved their economy of movement score up to the third repetition and group 3 up to the sixth repetition (Friedman's tests, P <0.05). Experienced surgeons (group 1) demonstrated best performance parameters, followed by group 2 and group 3 (Mann-Whitney test P <0.05). Different learning curves existed for surgeons with different laparoscopic background. The familiarization rate on the simulator was proportional to the operative experience of the surgeons. Experienced surgeons demonstrated best laparoscopic performance on the simulator, followed by those with intermediate experience and the beginners. These differences indicate that the scoring system of MIST-VR is sensitive and specific to measuring skills relevant for laparoscopic surgery.

Head Trauma in Mixed Martial Arts.

PubMed

Hutchison, Michael G; Lawrence, David W; Cusimano, Michael D; Schweizer, Tom A

2014-06-01

Mixed martial arts (MMA) is a full combative sport with a recent global increase in popularity despite significant scrutiny from medical associations. To date, the empirical research of the risk of head injuries associated with this sport is limited. Youth and amateur participation is growing, warranting investigation into the burden and mechanism of injuries associated with this sport. (1) To determine the incidence, risk factors, and characteristics of knockouts (KOs) and technical knockouts (TKOs) from repetitive strikes in professional MMA; and (2) to identify the mechanisms of head trauma and the situational factors that lead to KOs and TKOs secondary to repetitive strikes through video analysis. Descriptive epidemiology study. Competition data and video records for all KOs and TKOs from numbered Ultimate Fighting Championship MMA events (n = 844) between 2006 to 2012. Analyses included (1) multivariate logistic regression to investigate factors associated with an increased risk of sustaining a KO or TKO secondary to repetitive strikes and (2) video analysis of all KOs and TKOs secondary to repetitive strikes with descriptive statistics. During the study period, the KO rate was 6.4 per 100 athlete-exposures (AEs) (12.7% of matches), and the rate of TKOs secondary to repetitive strikes was 9.5 per 100 AEs (19.1% of matches), for a combined incidence of match-ending head trauma of 15.9 per 100 AEs (31.9% of matches). Logistic regression identified that weight class, earlier time in a round, earlier round in a match, and older age were risk factors for both KOs and TKOs secondary to repetitive strikes. Match significance and previously sustained KOs or TKOs were also risk factors for KOs. Video analysis identified that all KOs were the result of direct impact to the head, most frequently a strike to the mandibular region (53.9%). The average time between the KO-strike and match stoppage was 3.5 seconds (range, 0-20 seconds), with losers sustaining an average of 2.6 additional strikes (range, 0-20 strikes) to the head. For TKOs secondary to strikes, in the 30-second interval immediately preceding match stoppage, losers sustained, on average, 18.5 strikes (range, 5-46 strikes), with 92.3% of these being strikes to the head. Rates of KOs and TKOs in MMA are higher than previously reported rates in other combative and contact sports. Public health authorities and physicians should be cognizant of the rates and mechanisms of head trauma. Preventive measures to lessen the risks of head trauma for those who elect to participate in MMA are described. © 2014 The Author(s).

flexTMS--a novel repetitive transcranial magnetic stimulation device with freely programmable stimulus currents.

PubMed

Gattinger, Norbert; Moessnang, Georg; Gleich, Bernhard

2012-07-01

Transcranial magnetic stimulation (TMS) is able to noninvasively excite neuronal populations due to brief magnetic field pulses. The efficiency and the characteristics of stimulation pulse shapes influence the physiological effect of TMS. However, commercial devices allow only a minimum of control of different pulse shapes. Basically, just sinusoidal and monophasic pulse shapes with fixed pulse widths are available. Only few research groups work on TMS devices with controllable pulse parameters such as pulse shape or pulse width. We describe a novel TMS device with a full-bridge circuit topology incorporating four insulated-gate bipolar transistor (IGBT) modules and one energy storage capacitor to generate arbitrary waveforms. This flexible TMS (flexTMS ) device can generate magnetic pulses which can be adjusted with respect to pulse width, polarity, and intensity. Furthermore, the equipment allows us to set paired pulses with a variable interstimulus interval (ISI) from 0 to 20 ms with a step size of 10  μs. All user-defined pulses can be applied continually with repetition rates up to 30 pulses per second (pps) or, respectively, up to 100 pps in theta burst mode. Offering this variety of flexibility, flexTMS will allow the enhancement of existing TMS paradigms and novel research applications.

Femtosecond, two-photon laser-induced-fluorescence imaging of atomic oxygen in an atmospheric-pressure plasma jet

NASA Astrophysics Data System (ADS)

Schmidt, Jacob B.; Sands, Brian L.; Kulatilaka, Waruna D.; Roy, Sukesh; Scofield, James; Gord, James R.

2015-06-01

Femtosecond, two-photon-absorption laser-induced-fluorescence (fs-TALIF) spectroscopy is employed to measure space- and time-resolved atomic-oxygen distributions in a nanosecond, repetitively pulsed, externally grounded, atmospheric-pressure plasma jet flowing helium with a variable oxygen admixture. The high-peak-intensity, low-average-energy femtosecond pulses result in increased TALIF signal with reduced photolytic inferences. This allows 2D imaging of absolute atomic-oxygen number densities ranging from 5.8   ×   1015 to 2.0   ×   1012cm-3 using a cooled CCD with an external intensifier. Xenon is used for signal and imaging-system calibrations to quantify the atomic-oxygen fluorescence signal. Initial results highlight a transition in discharge morphology from annular to filamentary, corresponding with a change in plasma chemistry from ozone to atomic oxygen production, as the concentration of oxygen in the feed gas is changed at a fixed voltage-pulse-repetition rate. In this configuration, significant concentrations of reactive oxygen species may be remotely generated by sustaining an active discharge beyond the confines of the dielectric capillary, which may benefit applications that require large concentrations of reactive oxygen species such as material processing or biomedical devices.

RSI: oxygen consumption, blood flow, and reoxygenation in patients suffering RSI measured by noninvasive optical spectroscopy

NASA Astrophysics Data System (ADS)

Thijssen, Dick H. J.; van Uden, Caro J. T.; Krijgsman, Hans; Colier, Willy N. J. M.

2003-07-01

Background: Repetitive Strain Injury (RSI) is a major problem in nowadays health care and creates high financial costs and personal distress. Average prevalence rates in the Netherlands vary from 20-40% of the working population. Insight into the patho-physiological mechanism of RSI is important in order to establish adequate treatment and prevention programs. Objective: The aim of this study was to gain insight in muscle oxygen consumption (mVO2), blood flow (BF), and reoxygenation (ReOx) in the forearm of computer workers with stage III Repetitive Strain Injury (RSI). Method: We have used continuous wave infrared spectroscopy (NIRS) to measure these variables. Measurements were conducted on the extensor and flexor muscle in both arms as well in RSI-patients (n=10) as in control subjects (n=21). A protocol of increased isometric repetitive contraction in a handgrip ergonometer was used with increasing levels of strength. Results: mVO2 in the extensor muscle in RSI-subjects (dominant side) was increased compared to control subjects and compared to the non-dominant side (p<0.05). ReOx was not increased in RSI (dominant side-extensor muscle). However, there was a tendency towards statistical significance (p=0.065). BF in rest was equal in both groups, however after exercise it tended to be increased. Half-time recovery (T ») was measured during only one part of the protocol and it was significantly increased (p<0.05). Conclusion: mVO2 in RSI is impaired. BF and ReOx did not show difference between both groups. Future research should aim at a microvascular dysfunction in RSI.

Development of a cryogenic hydrogen microjet for high-intensity, high-repetition rate experiments

DOE PAGES

Kim, J. B.; Göde, S.; Glenzer, S. H.

2016-08-19

The advent of high-intensity, high-repetition-rate lasers has led to the need for replenishing targets of interest for high energy density sciences. We describe the design and characterization of a cryogenic microjet source, which can deliver a continuous stream of liquid hydrogen with a diameter of a few microns. The jet has been imaged at 1 μm resolution by shadowgraphy with a short pulse laser. In conclusion, the pointing stability has been measured at well below a mrad, for a stable free-standing filament of solid-density hydrogen.

A high repetition deterministic single ion source

NASA Astrophysics Data System (ADS)

Sahin, C.; Geppert, P.; Müllers, A.; Ott, H.

2017-12-01

We report on a deterministic single ion source with high repetition rate and high fidelity. The source employs a magneto-optical trap, where ultracold rubidium atoms are photoionized. The electrons herald the creation of a corresponding ion, whose timing information is used to manipulate its trajectory in flight. We demonstrate an ion rate of up to 4× {10}4 {{{s}}}-1 and achieve a fidelity for single ion operation of 98%. The technique can be used for all atomic species, which can be laser-cooled, and opens up new applications in ion microscopy, ion implantation and surface spectroscopy.

Multi-Physics Analysis of the Fermilab Booster RF Cavity

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

Awida, M.; Reid, J.; Yakovlev, V.

After about 40 years of operation the RF accelerating cavities in Fermilab Booster need an upgrade to improve their reliability and to increase the repetition rate in order to support a future experimental program. An increase in the repetition rate from 7 to 15 Hz entails increasing the power dissipation in the RF cavities, their ferrite loaded tuners, and HOM dampers. The increased duty factor requires careful modelling for the RF heating effects in the cavity. A multi-physic analysis investigating both the RF and thermal properties of Booster cavity under various operating conditions is presented in this paper.

Scintillator-based transverse proton beam profiler for laser-plasma ion sources.

PubMed

Dover, N P; Nishiuchi, M; Sakaki, H; Alkhimova, M A; Faenov, A Ya; Fukuda, Y; Kiriyama, H; Kon, A; Kondo, K; Nishitani, K; Ogura, K; Pikuz, T A; Pirozhkov, A S; Sagisaka, A; Kando, M; Kondo, K

2017-07-01

A high repetition rate scintillator-based transverse beam profile diagnostic for laser-plasma accelerated proton beams has been designed and commissioned. The proton beam profiler uses differential filtering to provide coarse energy resolution and a flexible design to allow optimisation for expected beam energy range and trade-off between spatial and energy resolution depending on the application. A plastic scintillator detector, imaged with a standard 12-bit scientific camera, allows data to be taken at a high repetition rate. An algorithm encompassing the scintillator non-linearity is described to estimate the proton spectrum at different spatial locations.

A racetrack mode-locked silicon evanescent laser.

PubMed

Fang, Alexander W; Koch, Brian R; Gan, Kian-Giap; Park, Hyundai; Jones, Richard; Cohen, Oded; Paniccia, Mario J; Blumenthal, Daniel J; Bowers, John E

2008-01-21

By utilizing a racetrack resonator topography, an on-chip mode locked silicon evanescent laser (ML-SEL) is realized that is independent of facet polishing. This enables integration with other devices on silicon and precise control of the ML-SEL's repetition rate through lithographic definition of the cavity length. Both passive and hybrid mode-locking have been achieved with transform limited, 7 ps pulses emitted at a repetition rate of 30 GHz. Jitter and locking range are measured under hybrid mode locking with a minimum absolute jitter and maximum locking range of 364 fs, and 50 MHz, respectively.

Power scaling of supercontinuum seeded megahertz-repetition rate optical parametric chirped pulse amplifiers.

PubMed

Riedel, R; Stephanides, A; Prandolini, M J; Gronloh, B; Jungbluth, B; Mans, T; Tavella, F

2014-03-15

Optical parametric chirped-pulse amplifiers with high average power are possible with novel high-power Yb:YAG amplifiers with kW-level output powers. We demonstrate a compact wavelength-tunable sub-30-fs amplifier with 11.4 W average power with 20.7% pump-to-signal conversion efficiency. For parametric amplification, a beta-barium borate crystal is pumped by a 140 W, 1 ps Yb:YAG InnoSlab amplifier at 3.25 MHz repetition rate. The broadband seed is generated via supercontinuum generation in a YAG crystal.

HiLASE: development of fully diode pumped disk lasers with high average power

NASA Astrophysics Data System (ADS)

Divoky, M.; Smrz, M.; Chyla, M.; Sikocinski, P.; Severova, P.; Novák, O.; Huynh, J.; Nagisetty, S. S.; Miura, T.; Liberatore, C.; Pilař, J.; Slezak, O.; Sawicka, M.; Jambunathan, V.; Gemini, L.; Vanda, J.; Svabek, R.; Endo, A.; Lucianetti, A.; Rostohar, D.; Mason, P. D.; Phillips, P. J.; Ertel, K.; Banerjee, S.; Hernandez-Gomez, C.; Collier, J. L.; Mocek, T.

2015-02-01

An overview of Czech national R&D project HiLASE (High average power pulsed LASEr) is presented. The HiLASE project aims at development of pulsed DPSSL for hi-tech industrial applications. HiLASE will be a user oriented facility with several laser systems with output parameters ranging from a few picosecond pulses with energy of 5 mJ to 0.5 J and repetition rate of 1-100 kHz (based on thin disk technology) to systems with 100 J output energy in nanosecond pulses with repetition rate of 10 Hz (based on multi-slab technology).

Actively mode-locked erbium fiber ring laser using a Fabry-Perot semiconductor modulator as mode locker and tunable filter

NASA Astrophysics Data System (ADS)

Li, Shenping; Chan, K. T.

1999-05-01

A wavelength-tunable actively mode-locked erbium fiber ring laser was demonstrated using a Fabry-Perot semiconductor modulator. The modulator played the simultaneous roles of an intensity mode locker and a tunable optical filter. Stable single- or dual-wavelength nearly transform-limited picosecond pulses at gigabit repetition rates were generated. Continuous wavelength tuning was achieved by simply controlling the temperature of the modulator. Pulse train with a repetition rate up to 19.93 GHz (eight times the driving frequency) was obtained by using rational harmonic mode-locking technique.

High-repetition-rate widely tunable LiF : \\mathbf{\\mathsf{F}}_\\mathbf{\\mathsf{2}}^{-} color center lasers

NASA Astrophysics Data System (ADS)

Men, Shaojie; Liu, Zhaojun; Cong, Zhenhua; Rao, Han; Zhang, Sasa; Liu, Yang; Zverev, Petr G.; Konyushkin, Vasily A.; Zhang, Xingyu

2016-02-01

High-repetition-rate tunable LiF:\\text{F}2- color center lasers pumped by quasi-continuous-wave diode-side-pumped acousto-optically Q-switched Nd:YAG laser are demonstrated. Littrow-grating and Littman-grating tuning schemes are studied respectively. In the Littrow-grating scheme, the tuning range was 1085 nm to 1275 nm, and the maximal average output power was 275 mW. In the Littman-grating scheme, the tuning range was 1105.5 nm to 1215.5 nm, and the maximal average output power was 135 mW.

Repetition increases false recollection in older people.

PubMed

Pitarque, Alfonso; Sales, Alicia; Meléndez, Juan Carlos; Algarabel, Salvador

2015-02-01

Aging is accompanied by an increase in false alarms on recognition tasks, and these false alarms increase with repetition in older people (but not in young people). Traditionally, this increase was thought to be due to a greater use of familiarity in older people, but it was recently pointed out that false alarms also have a clear recollection component in these people. The main objective of our study is to analyze whether the expected increase in the rate of false alarms in older people due to stimulus repetition is produced by an inadequate use of familiarity, recollection, or both processes. To do so, we carried out an associative recognition experiment using pairs of words and pairs of images (faces associated with everyday contexts), in which we analyzed whether the repetition of some of the pairs increases the rate of false alarms in older people (compared to what was found in a sample of young people), and whether this increase is due to familiarity or recollection (using a remember-know paradigm). Our results show that the increase in false alarms in older people due to repetition is produced by false recollection, calling into question both dual and single-process models of recognition. Also, older people falsely recollect details of never studied stimuli, a clear case of perceptual illusions. These results are better explained in terms of source-monitoring errors, mediated by people's retrieval expectations. © 2014 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

Effects of Variable Resistance Using Chains on Bench Throw Performance in Trained Rugby Players.

PubMed

Godwin, Mark S; Fernandes, John F T; Twist, Craig

2018-04-01

Godwin, MS, Fernandes, JFT, and Twist, C. Effects of variable resistance using chains on bench throw performance in trained rugby players. J Strength Cond Res 32(4): 950-954, 2018-This study sought to determine the effects of variable resistance using chain resistance on bench throw performance. Eight male rugby union players (19.4 ± 2.3 years, 88.8 ± 6.0 kg, 1RM 105.6 ± 17.0 kg) were recruited from a national league team. In a randomized crossover design, participant's performed 3 bench throws at 45% one repetition maximum (1RM) at a constant load (no chains) or a variable load (30% 1RM constant load and 15% 1RM variable load; chains) with 7 days between conditions. For each repetition, the peak and mean velocity, peak power, peak acceleration, and time to peak velocity were recorded. Differences in peak and mean power were very likely trivial and unclear between the chain and no chain conditions, respectively. Possibly greater peak and likely greater mean bar velocity were accompanied by likely to most likely greater bar velocity between 50 and 400 ms from initiation of bench press in the chain condition compared with the no chain condition. Accordingly, bar acceleration was very likely greater in the chain condition compared with the no chain condition. In conclusion, these results show that the inclusion of chain resistance can acutely enhance several variables in the bench press throw and gives support to this type of training.

Fluorescence advantages with microscopic spatiotemporal control

NASA Astrophysics Data System (ADS)

Goswami, Debabrata; Roy, Debjit; De, Arijit K.

2013-03-01

We present a clever design concept of using femtosecond laser pulses in microscopy by selective excitation or de-excitation of one fluorophore over the other overlapping one. Using either a simple pair of femtosecond pulses with variable delay or using a train of laser pulses at 20-50 Giga-Hertz excitation, we show controlled fluorescence excitation or suppression of one of the fluorophores with respect to the other through wave-packet interference, an effect that prevails even after the fluorophore coherence timescale. Such an approach can be used both under the single-photon excitation as well as in the multi-photon excitation conditions resulting in effective higher spatial resolution. Such high spatial resolution advantage with broadband-pulsed excitation is of immense benefit to multi-photon microscopy and can also be an effective detection scheme for trapped nanoparticles with near-infrared light. Such sub-diffraction limit trapping of nanoparticles is challenging and a two-photon fluorescence diagnostics allows a direct observation of a single nanoparticle in a femtosecond high-repetition rate laser trap, which promises new directions to spectroscopy at the single molecule level in solution. The gigantic peak power of femtosecond laser pulses at high repetition rate, even at low average powers, provide huge instantaneous gradient force that most effectively result in a stable optical trap for spatial control at sub-diffraction limit. Such studies have also enabled us to explore simultaneous control of internal and external degrees of freedom that require coupling of various control parameters to result in spatiotemporal control, which promises to be a versatile tool for the microscopic world.

Motor unit activity when young and old adults perform steady contractions while supporting an inertial load

PubMed Central

Gould, Jeffrey R.; Enoka, Roger M.

2013-01-01

The purpose of the study was to compare the discharge characteristics of biceps brachii motor units of young and old adults when they performed steady, submaximal contractions while the arm supported different inertial loads. Young (28 ± 4 yr; n = 16) and old (75 ± 4 yr; n = 14) adults performed steady contractions with the elbow flexors at target forces set at either small (11.7 ± 4.4% maximum) or large (17.8 ± 6.5% maximum) differences below the recruitment threshold force of the motor unit (n = 40). The task was to maintain an elbow angle at 1.57 rad until the motor unit was recruited and discharged action potentials for ∼120 s. Time to recruitment was longer for the larger target force difference (187 ± 227 s vs. 23 ± 46 s, P < 0.001). Once recruited, motor units discharged action potentials either repetitively or intermittently, with a greater proportion of motor units exhibiting the repetitive pattern for old adults. Discharge rate at recruitment and during the steady contraction was similar for the two target force differences for old adults but was greater for the small target force difference for young adults. Discharge variability was similar at recruitment for the two age groups but less for the old adults during the steady contraction. The greatest difference between the present results and those reported previously when the arm pulled against a rigid restraint was that old adults modulated discharge rate less than young adults across the two contraction intensities for both load types. PMID:23221403

Biology and applications of human minisatellite loci.

PubMed

Armour, J A; Jeffreys, A J

1992-12-01

Highly repetitive minisatellites' include the most variable human loci described to date. They have proved invaluable in a wide variety of genetic analyses, and despite some controversies surrounding their practical implementation, have been extensively adopted in civil and forensic casework. Molecular analysis of internal allelic structure has provided detailed insights into the repeat-unit turnover mechanisms operating in germline mutations, which are ultimately responsible for the extreme variability seen at these loci.

Recent transmission of drug-resistant Mycobacterium tuberculosis in a prison population in southern Brazil.

PubMed

Reis, Ana Julia; David, Simone Maria Martini de; Nunes, Luciana de Souza; Valim, Andreia Rosane de Moura; Possuelo, Lia Gonçalves

2016-01-01

We conducted a cross-sectional, retrospective study, characterized by classical and molecular epidemiology, involving M. tuberculosis isolates from a regional prison in southern Brazil. Between January of 2011 and August of 2014, 379 prisoners underwent sputum smear microscopy and culture; 53 (13.9%) were diagnosed with active tuberculosis. Of those, 8 (22.9%) presented with isoniazid-resistant tuberculosis. Strain genotyping was carried out by 15-locus mycobacterial interspersed repetitive unit-variable-number tandem-repeat analysis; 68.6% of the patients were distributed into five clusters, and 87.5% of the resistant cases were in the same cluster. The frequency of drug-resistant tuberculosis cases and the rate of recent transmission were high. Our data suggest the need to implement an effective tuberculosis control program within the prison system. RESUMO Estudo transversal, retrospectivo, com isolados de M. tuberculosis de pacientes de um presídio regional no sul do Brasil, caracterizado através de epidemiologia clássica e molecular. Entre janeiro de 2011 e agosto de 2014, 379 detentos foram submetidos a baciloscopia e cultura, sendo 53 (13,9%) diagnosticados com tuberculose ativa. Desses, 8 (22,9%) apresentavam tuberculose resistente a isoniazida. A genotipagem das cepas foi realizada por 15-locus mycobacterial interspersed repetitive units-variable number of tandem repeat analysis; 68,6% dos pacientes estavam distribuídos em cinco clusters, e 87,5% dos casos resistentes estavam em um mesmo cluster. Verificou-se uma frequência elevada de casos de resistência e alta taxa de transmissão recente. Estes dados sugerem a necessidade da implantação de um programa efetivo de controle da tuberculose no sistema prisional.

Phonological neighborhood and word frequency effects in the stuttered disfluencies of children who stutter.

PubMed

Anderson, Julie D

2007-02-01

The purpose of this study was to examine (a) the role of neighborhood density (number of words that are phonologically similar to a target word) and frequency variables on the stuttering-like disfluencies of preschool children who stutter, and (b) whether these variables have an effect on the type of stuttering-like disfluency produced. A 500+ word speech sample was obtained from each participant (N = 15). Each stuttered word was randomly paired with the firstly produced word that closely matched it in grammatical class, familiarity, and number of syllables/phonemes. Frequency, neighborhood density, and neighborhood frequency values were obtained for the stuttered and fluent words from an online database. Findings revealed that stuttered words were lower in frequency and neighborhood frequency than fluent words. Words containing part-word repetitions and sound prolongations were also lower in frequency and/or neighborhood frequency than fluent words, but these frequency variables did not have an effect on single-syllable word repetitions. Neighborhood density failed to influence the susceptibility of words to stuttering, as well as the type of stuttering-like disfluency produced. In general, findings suggest that neighborhood and frequency variables not only influence the fluency with which words are produced in speech, but also have an impact on the type of stuttering-like disfluency produced.

Brief Report: Glutamate Transporter Gene ("SLC1A1") Single Nucleotide Polymorphism (rs301430) and Repetitive Behaviors and Anxiety in Children with Autism Spectrum Disorder

ERIC Educational Resources Information Center

Gadow, Kenneth D.; Roohi, Jasmin; DeVincent, Carla J.; Kirsch, Sarah; Hatchwell, Eli

2010-01-01

Investigated association of single nucleotide polymorphism (SNP) rs301430 in glutamate transporter gene ("SLC1A1") with severity of repetitive behaviors (obsessive-compulsive behaviors, tics) and anxiety in children with autism spectrum disorder (ASD). Mothers and/or teachers completed a validated DSM-IV-referenced rating scale for 67 children…

Design of Warped Stretch Transform

PubMed Central

Mahjoubfar, Ata; Chen, Claire Lifan; Jalali, Bahram

2015-01-01

Time stretch dispersive Fourier transform enables real-time spectroscopy at the repetition rate of million scans per second. High-speed real-time instruments ranging from analog-to-digital converters to cameras and single-shot rare-phenomena capture equipment with record performance have been empowered by it. Its warped stretch variant, realized with nonlinear group delay dispersion, offers variable-rate spectral domain sampling, as well as the ability to engineer the time-bandwidth product of the signal’s envelope to match that of the data acquisition systems. To be able to reconstruct the signal with low loss, the spectrotemporal distribution of the signal spectrum needs to be sparse. Here, for the first time, we show how to design the kernel of the transform and specifically, the nonlinear group delay profile dictated by the signal sparsity. Such a kernel leads to smart stretching with nonuniform spectral resolution, having direct utility in improvement of data acquisition rate, real-time data compression, and enhancement of ultrafast data capture accuracy. We also discuss the application of warped stretch transform in spectrotemporal analysis of continuous-time signals. PMID:26602458

Comprehension priming as rational expectation for repetition: Evidence from syntactic processing.

PubMed

Myslín, Mark; Levy, Roger

2016-02-01

Why do comprehenders process repeated stimuli more rapidly than novel stimuli? We consider an adaptive explanation for why such facilitation may be beneficial: priming is a consequence of expectation for repetition due to rational adaptation to the environment. If occurrences of a stimulus cluster in time, given one occurrence it is rational to expect a second occurrence closely following. Leveraging such knowledge may be particularly useful in online processing of language, where pervasive clustering may help comprehenders negotiate the considerable challenge of continual expectation update at multiple levels of linguistic structure and environmental variability. We test this account in the domain of structural priming in syntax, making use of the sentential complement-direct object (SC-DO) ambiguity. We first show that sentences containing SC continuations cluster in natural language, motivating an expectation for repetition of this structure. Second, we show that comprehenders are indeed sensitive to the syntactic clustering properties of their current environment. In a series of between-groups self-paced reading studies, we find that participants who are exposed to clusters of SC sentences subsequently process repetitions of SC structure more rapidly than participants who are exposed to the same number of SCs spaced in time, and attribute the difference to the learned degree of expectation for repetition. We model this behavior through Bayesian belief update, showing that (the optimal degree of) sensitivity to clustering properties of syntactic structures is indeed learnable through experience. Comprehension priming effects are thus consistent with rational expectation for repetition based on adaptation to the linguistic environment. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Comprehension priming as rational expectation for repetition: Evidence from syntactic processing

PubMed Central

Levy, Roger

2015-01-01

Why do comprehenders process repeated stimuli more rapidly than novel stimuli? We consider an adaptive explanation for why such facilitation may be beneficial: priming is a consequence of expectation for repetition due to rational adaptation to the environment. If occurrences of a stimulus cluster in time, given one occurrence it is rational to expect a second occurrence closely following. Leveraging such knowledge may be particularly useful in online processing of language, where pervasive clustering may help comprehenders negotiate the considerable challenge of continual expectation update at multiple levels of linguistic structure and environmental variability. We test this account in the domain of structural priming in syntax, making use of the sentential complement-direct object (SC-DO) ambiguity. We first show that sentences containing SC continuations cluster in natural language, motivating an expectation for repetition of this structure. Second, we show that comprehenders are indeed sensitive to the syntactic clustering properties of their current environment. In a series of between-groups self-paced reading studies, we find that participants who are exposed to clusters of SC sentences subsequently process repetitions of SC structure more rapidly than participants who are exposed to the same number of SCs spaced in time, and attribute the difference to the learned degree of expectation for repetition. We model this behavior through Bayesian belief update, showing that (the optimal degree of) sensitivity to clustering properties of syntactic structures is indeed learnable through experience. Comprehension priming effects are thus consistent with rational expectation for repetition based on adaptation to the linguistic environment. PMID:26605963

Optical generation and detection of gigahertz-frequency longitudinal and shear acoustic waves in liquids: Theory and experiment

NASA Astrophysics Data System (ADS)

Klieber, Christoph; Pezeril, Thomas; Andrieu, Stéphane; Nelson, Keith A.

2012-07-01

We describe an adaptation of picosecond laser ultrasonics tailored for study of GHz-frequency longitudinal and shear acoustic waves in liquids. Time-domain coherent Brillouin scattering is used to detect multicycle acoustic waves after their propagation through variable thickness liquid layers into a solid substrate. A specialized optical pulse shaping method is used to generate sequences of pulses whose repetition rate determines the acoustic frequency. The measurements reveal the viscoelastic liquid properties and also include signatures of the optical and acoustic cavities formed by the multilayer sample assembly. Modeling of the signals allows their features to be distinguished so that liquid properties can be extracted reliably. Longitudinal and shear acoustic wave data from glycerol and from the silicon oil DC704 are presented.

Impacts of obesity and stress on neuromuscular fatigue development and associated heart rate variability.

PubMed

Mehta, R K

2015-02-01

Obesity and stress are independently associated with decrements in neuromuscular functions. The present study examined the interplay of obesity and stress on neuromuscular fatigue and associated heart rate variability (HRV). Forty-eight non-obese (18.5

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

NASA Astrophysics Data System (ADS)

Schuback, N.; Flecken, M.; Maldonado, M. T.; Tortell, P. D.

2015-10-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation at PSII (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis, and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific, over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5 fold changes in the conversion factor coupling ETRRCII and carbon fixation (Φe:C / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light, and correlates with the expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and the conversion factor Φe:C / nPSII has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

Diurnal variation in the coupling of photosynthetic electron transport and carbon fixation in iron-limited phytoplankton in the NE subarctic Pacific

NASA Astrophysics Data System (ADS)

Schuback, Nina; Flecken, Mirkko; Maldonado, Maria T.; Tortell, Philippe D.

2016-02-01

Active chlorophyll a fluorescence approaches, including fast repetition rate fluorometry (FRRF), have the potential to provide estimates of phytoplankton primary productivity at an unprecedented spatial and temporal resolution. FRRF-derived productivity rates are based on estimates of charge separation in reaction center II (ETRRCII), which must be converted into ecologically relevant units of carbon fixation. Understanding sources of variability in the coupling of ETRRCII and carbon fixation provides physiological insight into phytoplankton photosynthesis and is critical for the application of FRRF as a primary productivity measurement tool. In the present study, we simultaneously measured phytoplankton carbon fixation and ETRRCII in the iron-limited NE subarctic Pacific over the course of a diurnal cycle. We show that rates of ETRRCII are closely tied to the diurnal cycle in light availability, whereas rates of carbon fixation appear to be influenced by endogenous changes in metabolic energy allocation under iron-limited conditions. Unsynchronized diurnal oscillations of the two rates led to 3.5-fold changes in the conversion factor between ETRRCII and carbon fixation (Kc / nPSII). Consequently, diurnal variability in phytoplankton carbon fixation cannot be adequately captured with FRRF approaches if a constant conversion factor is applied. Utilizing several auxiliary photophysiological measurements, we observed that a high conversion factor is associated with conditions of excess light and correlates with the increased expression of non-photochemical quenching (NPQ) in the pigment antenna, as derived from FRRF measurements. The observed correlation between NPQ and Kc / nPSII requires further validation but has the potential to improve estimates of phytoplankton carbon fixation rates from FRRF measurements alone.

Comparison of PA imaging by narrow beam scanning and one-shot broad beam excitation

NASA Astrophysics Data System (ADS)

Xia, Jinjun; Wei, Chen-Wei; Huang, Lingyun; Pelivanov, I. M.; O'Donnell, Matthew

2011-03-01

Current systems designed for deep photoacoustic (PA) imaging typically use a low repetition rate, high power pulsed laser to provide a ns-scale pulse illuminating a large tissue volume. Acoustic signals recorded on each laser firing can be used to reconstruct a complete 2-D (3-D) image of sources of heat release within that region. Using broad-beam excitation, the maximum frame rate of the imaging system is restricted by the pulse repetition rate of the laser. An alternate illumination approach is proposed based on fast scanning by a low energy (~ 1 mJ) high repetition rate (up to a few kHz) narrow laser beam (~1 mm) along the tissue surface over a region of interest. A final PA image is produced from the summation of individual PA images reconstructed at each laser beam position. This concept can take advantage of high repetition rate fiber lasers to create PA images with much higher frame rates than current systems, enabling true real-time integration of photoacoustics with ultrasound imaging. As an initial proof of concept, we compare conventional broad beam illumination to a scanned beam approach in a simple model system. Two transparent teflon tubes with diameters of 1.6 mm and 0.8 mm were filled with ink having an absorption coefficient of 5 cm-1. These tubes were buried inside chicken breast tissue acting as an optical scattering medium. They were separated by 3 mm or 10 mm to test spatial and contrast resolution for the two scan formats. The excitation wavelength was 700 nm. The excitation source is a traditional OPO pumped by a Q-switched Nd:YAG laser with doubler. Photoacoustic images were reconstructed using signals from a small, scanned PVDF transducer acting as an acoustic array. Two different illumination schemes were compared: one was 15 mm x 10 mm in cross section and acted as the broad beam; the other was 5 mm x 2 mm in cross section (15 times smaller than the broad beam case) and was scanned over an area equivalent to broad beam illumination. Multiple images obtained during narrow beam scanning were added together to form one PA image equivalent to the single-shot broad beam one. Results of the phantom study indicate that PA images formed by narrow beam scanning excitation can be equivalent to one shot broad beam illumination in signal to noise ratio and spatial resolution. Future studies will focus on high repetition-rate laser sources and scan formats appropriate for real-time, integrated deep photoacoustic/ultrasonic imaging.

High-power, high-repetition-rate performance characteristics of β-BaB₂O₄ for single-pass picosecond ultraviolet generation at 266 nm.

PubMed

Kumar, S Chaitanya; Casals, J Canals; Wei, Junxiong; Ebrahim-Zadeh, M

2015-10-19

We report a systematic study on the performance characteristics of a high-power, high-repetition-rate, picosecond ultraviolet (UV) source at 266 nm based on β-BaB2O4 (BBO). The source, based on single-pass fourth harmonic generation (FHG) of a compact Yb-fiber laser in a two-crystal spatial walk-off compensation scheme, generates up to 2.9 W of average power at 266 nm at a pulse repetition rate of ~80 MHz with a single-pass FHG efficiency of 35% from the green to UV. Detrimental issues such as thermal effects have been studied and confirmed by performing relevant measurements. Angular and temperature acceptance bandwidths in BBO for FHG to 266 nm are experimentally determined, indicating that the effective interaction length is limited by spatial walk-off and thermal gradients under high-power operation. The origin of dynamic color center formation due to two-photon absorption in BBO is investigated by measurements of intensity-dependent transmission at 266 nm. Using a suitable theoretical model, two-photon absorption coefficients as well as the color center densities have been estimated at different temperatures. The measurements show that the two-photon absorption coefficient in BBO at 266 nm is ~3.5 times lower at 200°C compared to that at room temperature. The long-term power stability as well as beam pointing stability is analyzed at different output power levels and focusing conditions. Using cylindrical optics, we have circularized the generated elliptic UV beam to a circularity of >90%. To our knowledge, this is the first time such high average powers and temperature-dependent two-photon absorption measurements at 266 nm are reported at repetition rates as high as ~80 MHz.

Probing ultra-fast processes with high dynamic range at 4th-generation light sources: Arrival time and intensity binning at unprecedented repetition rates

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

Kovalev, S.; Green, B.; Golz, T.

Here, understanding dynamics on ultrafast timescales enables unique and new insights into important processes in the materials and life sciences. In this respect, the fundamental pump-probe approach based on ultra-short photon pulses aims at the creation of stroboscopic movies. Performing such experiments at one of the many recently established accelerator-based 4th-generation light sources such as free-electron lasers or superradiant THz sources allows an enormous widening of the accessible parameter space for the excitation and/or probing light pulses. Compared to table-top devices, critical issues of this type of experiment are fluctuations of the timing between the accelerator and external laser systemsmore » and intensity instabilities of the accelerator-based photon sources. Existing solutions have so far been only demonstrated at low repetition rates and/or achieved a limited dynamic range in comparison to table-top experiments, while the 4th generation of accelerator-based light sources is based on superconducting radio-frequency technology, which enables operation at MHz or even GHz repetition rates. In this article, we present the successful demonstration of ultra-fast accelerator-laser pump-probe experiments performed at an unprecedentedly high repetition rate in the few-hundred-kHz regime and with a currently achievable optimal time resolution of 13 fs (rms). Our scheme, based on the pulse-resolved detection of multiple beam parameters relevant for the experiment, allows us to achieve an excellent sensitivity in real-world ultra-fast experiments, as demonstrated for the example of THz-field-driven coherent spin precession.« less

The rate of repeating X-rays in the medical centers of Jenin District/Palestine and how to reduce patient exposure to radiation

NASA Astrophysics Data System (ADS)

Assi, Abed Al Nasser

2018-03-01

Reduction of the patient's received radiation dose to as low as reasonably achievable (ALARA) is based on recommendations of radiation protection organizations such as the International Commission on Radiological Protection (ICRP) and the National Radiological Protection Board (NRPB). The aim of this study was to explore the frequency and characteristics of rejected / repeated radiographic films in governmental and private centers in Jenin city. The radiological centers were chosen based on their high volume of radiographic studies. The evaluation was carried out over a period of four months. The collected data were compiled at the end of each week and entered into a computer for analysis at the end of study. Overall 5000 films (images) were performed in four months, The average repeat rate of radiographic images was 10% (500 films). Repetition rate was the same for both thoracic and abdominal images (42%). The main reason for repeating imaging was inadequate imaging quality (58.2%) and poor film processing (38%). Human error was the most likely reason necessitating the repetition of the radiographs (48 %). Infant and children groups comprised 85% of the patient population that required repetition of the radiographic studies. In conclusion, we have a higher repetition rate of imaging studies compared to the international standards (10% vs. 4-6%, respectively). This is especially noticeable in infants and children, and mainly attributed to human error in obtaining and processing images. This is an important issue that needs to be addressed on a national level due to the ill effects associated with excessive exposure to radiation especially in children, and to reduce cost of the care delivered.

Improvement of two-photon microscopic imaging in deep regions of living mouse brains by utilizing a light source based on an electrically controllable gain-switched laser diode

NASA Astrophysics Data System (ADS)

Sawada, Kazuaki; Kawakami, Ryosuke; Fang, Yi-Cheng; Hung, Jui-Hung; Kozawa, Yuichi; Otomo, Kohei; Sato, Shunichi; Yokoyama, Hiroyuki; Nemoto, Tomomi

2018-02-01

In vivo two-photon microscopy is an advantageous technique for observing living mouse brains at high spatial resolutions. We previously used a 1064 nm high-power light source based on an electrically controllable gain-switched laser diode (maximum power: 4 W, repetition rate: 10 MHz, pulse width: 7.5 picoseconds) and successfully visualized EYFP expressing neurons at deeper regions in H-line mouse brains under living conditions. However, severe damages were frequently observed when the laser power after the objective lens was over 600 mW, suggesting that a higher average power might not be suitable for visualizing neural structures and functions at deep regions. To increase fluorescent signals as a strategy to avoid such invasions, here, we evaluated the effects of the excitation laser parameters such as the repetition rate (5 - 10 MHz), or the peak power, at the moderate average powers (10 - 500 mW), by taking the advantage that this electrically controllable light source could be used to change the repetition rate independently from the average power or the pulse width. The fluorescent signals of EYFP at layer V of the cerebral cortex were increased by approximately twofold when the repetition rate was decreased from 10 MHz to 5 MHz at the same average power. We also confirmed similar effects in the EYFP solution (335 μM) and fixed brain slices. These results suggest that in vivo two-photon microscopic imaging might be improved by increasing the peak power at the same average power while avoiding the severe damages in living brains.

Full stabilization and characterization of an optical frequency comb from a diode-pumped solid-state laser with GHz repetition rate.

PubMed

Hakobyan, Sargis; Wittwer, Valentin J; Brochard, Pierre; Gürel, Kutan; Schilt, Stéphane; Mayer, Aline S; Keller, Ursula; Südmeyer, Thomas

2017-08-21

We demonstrate the first self-referenced full stabilization of a diode-pumped solid-state laser (DPSSL) frequency comb with a GHz repetition rate. The Yb:CALGO DPSSL delivers an average output power of up to 2.1 W with a typical pulse duration of 96 fs and a center wavelength of 1055 nm. A carrier-envelope offset (CEO) beat with a signal-to-noise ratio of 40 dB (in 10-kHz resolution bandwidth) is detected after supercontinuum generation and f-to-2f interferometry directly from the output of the oscillator, without any external amplification or pulse compression. The repetition rate is stabilized to a reference synthesizer with a residual integrated timing jitter of 249 fs [10 Hz - 1 MHz] and a relative frequency stability of 10 -12 /s. The CEO frequency is phase-locked to an external reference via pump current feedback using home-built modulation electronics. It achieves a loop bandwidth of ~150 kHz, which results in a tight CEO lock with a residual integrated phase noise of 680 mrad [1 Hz - 1 MHz]. We present a detailed characterization of the GHz frequency comb that combines a noise analysis of the repetition rate f rep , of the CEO frequency f CEO , and of an optical comb line at 1030 nm obtained from a virtual beat with a narrow-linewidth laser at 1557 nm using a transfer oscillator. An optical comb linewidth of about 800 kHz is assessed at 1-s observation time, for which the dominant noise sources of f rep and f CEO are identified.

A versatile, C-band spanning, high repetition rate, cascaded four wave mixing based multi-wavelength source

NASA Astrophysics Data System (ADS)

Vikram, B. S.; Prakash, Roopa; K. P., Nagarjun; Selvaraja, Shankar Kumar; Supradeepa, V. R.

2018-02-01

Demand for bandwidth in optical communications necessitates the development of scalable transceivers that cater to these needs. For this, in DWDM systems with/without Superchannels, the optical source needs to provide a large number of optical carriers. The conventional method of utilizing separate lasers makes the system bulky and inefficient. A multi-wavelength source which spans the entire C-band with sufficient power is needed to replace individual lasers. In addition, multi-wavelength sources at high repetition rates are necessary in various applications such as spectroscopy, astronomical spectrograph calibration, microwave photonics and arbitrary waveform generation. Here, we demonstrate a novel technique for equalized, multi-wavelength source generation which generates over 160 lines at 25GHz repetition rate, spanning the entire C-band with total power >700mW. A 25GHz Comb with 16 lines is generated around 1550nm starting with two individual lasers using a system of directly driven, cascaded intensity and phase modulators. This is then amplified to >1W using an optimized, Erbium-Ytterbium co-doped fiber amplifier. Subsequently, they are passed through Highly NonLinear Fiber at its zero-dispersion wavelength. Through cascaded Four Wave Mixing, a ten-fold increase in the number of lines is demonstrated. A bandwidth of 4.32 THz (174 lines, SNR>15 dB), covering the entire C-band is generated. Enhanced spectral broadening is enabled by two key aspects - Dual laser input provides the optimal temporal profile for spectral broadening while the comb generation prior to amplification enables greater power scaling by suppression of Brillouin scattering. The multi-wavelength source is extremely agile with tunable center frequency and repetition rate.

Mathematical modeling and spectrum analysis of the physiological patello-femoral pulse train produced by slow knee movement.

PubMed

Zhang, Y T; Frank, C B; Rangayyan, R M; Bell, G D

1992-09-01

Analysis of vibration signals emitted by the knee joint has the potential for the development of a noninvasive procedure for the diagnosis and monitoring of knee pathology. In order to obtain as much information as possible from the power density spectrum of the knee vibration signal, it is necessary to identify the physiological factors (or physiologically relevant parameters) that shape the spectrum. This paper presents a mathematical model for knee vibration signals, in particular the physiological patello-femoral pulse (PFP) train produced by slow knee movement. It demonstrates through the mathematical model that the repetition rate of the physiological PFP train introduces repeated peaks in the power spectrum, and that it affects the spectrum mainly at low frequencies. The theoretical results also show that the spectral peaks at multiples of the PFP repetition rate become more evident when the variance of the interpulse interval (IPI) is small, and that these spectral peaks shift toward higher frequencies with increasing PFP repetition rates. To evaluate the mathematical model, a simulation algorithm was developed, which generates PFP signals with adjustable repetition rate and IPI variance. Signals generated by simulation were seen to possess representative spectral characteristics typically observed in physiological PFP signals. This simulation procedure allows an interactive examination of several factors which affect the PFP train spectrum. Finally, in vivo measurements of physiological PFP signals of normal volunteers are presented. Results of simulations and analysis of signals recorded from human subjects support the mathematical model's prediction that the IPI statistics play a very significant role in determining the low-end power spectrum of the physiological PFP signal.(ABSTRACT TRUNCATED AT 250 WORDS)

Probing ultra-fast processes with high dynamic range at 4th-generation light sources: Arrival time and intensity binning at unprecedented repetition rates

DOE PAGES

Kovalev, S.; Green, B.; Golz, T.; ...

2017-03-06

Here, understanding dynamics on ultrafast timescales enables unique and new insights into important processes in the materials and life sciences. In this respect, the fundamental pump-probe approach based on ultra-short photon pulses aims at the creation of stroboscopic movies. Performing such experiments at one of the many recently established accelerator-based 4th-generation light sources such as free-electron lasers or superradiant THz sources allows an enormous widening of the accessible parameter space for the excitation and/or probing light pulses. Compared to table-top devices, critical issues of this type of experiment are fluctuations of the timing between the accelerator and external laser systemsmore » and intensity instabilities of the accelerator-based photon sources. Existing solutions have so far been only demonstrated at low repetition rates and/or achieved a limited dynamic range in comparison to table-top experiments, while the 4th generation of accelerator-based light sources is based on superconducting radio-frequency technology, which enables operation at MHz or even GHz repetition rates. In this article, we present the successful demonstration of ultra-fast accelerator-laser pump-probe experiments performed at an unprecedentedly high repetition rate in the few-hundred-kHz regime and with a currently achievable optimal time resolution of 13 fs (rms). Our scheme, based on the pulse-resolved detection of multiple beam parameters relevant for the experiment, allows us to achieve an excellent sensitivity in real-world ultra-fast experiments, as demonstrated for the example of THz-field-driven coherent spin precession.« less

Kansas squat test: a reliable indicator of short-term anaerobic power.

PubMed

Fry, Andrew C; Kudrna, Rebecca A; Falvo, Michael J; Bloomer, Richard J; Moore, Christopher A; Schilling, Brian K; Weiss, Lawrence W

2014-03-01

The purposes of this study were to establish stability reliability of a measure of lower-body anaerobic power, the Kansas squat test (KST), and to compare the KST with the commonly used Wingate anaerobic test (WAnT) for lower-body power. Fourteen resistance-trained men (mean ± SD; age = 24.2 ± 3.6 years) performed both the KST and the WAnT twice on separate occasions. The KST consisted of using an external dynamometer to measure mean repetition power while performing 15 repetitions of speed squats using 70% of 1 repetition maximum system mass (barbell + body mass), initiating each repetition at 6-second intervals. Repetition power, mean power for all 15 repetitions, and % fatigue for the KST were all reliable (intraclass correlation coefficient = 0.754-0.937; p ≤ 0.05). There were no differences between tests for the mean power for all repetitions or relative fatigue (p ≤ 0.05) and no significant differences between tests for any individual repetition (test × repetition interaction, p < 0.05). Although absolute values were different (p > 0.05), significant correlations were found between the KST and WAnT for mean (r = 0.752) and maximum (r = 0.775) test powers but not for relative fatigue (r = 0.174). Lactate (HLa) responses were greater for the WAnT compared with the KST. These data indicate that the KST is reliable for resistance-trained men, and that measures of maximum and mean test powers for the KST are highly correlated to those values for the WAnT, but fatigue rates and HLa responses were not correlated. It appears that the KST is a lifting-specific anaerobic power and power endurance test that emphasizes phosphagen metabolism and may be used to assess training-induced changes in lower-body power.

Electrocardiographic consequences of a peripatetic lifestyle in gray wolves (Canis lupus)

USGS Publications Warehouse

Constable, Peter; Hinchcliff, Ken; Demma, Nick; Callahan, Margaret; Dale, Bruce W.; Fox, Kevin; Adams, Layne G.; Wack, Ray; Kramer, Lynn

1998-01-01

Cardiac chamber enlargement and hypertrophy are normal physiologic responses to repetitive endurance exercise activity in human beings and domestic dogs. Whether similar changes occur in wild animals as a consequence of increased activity is unknown. We found that free-ranging gray wolves (Canis lupus, n=11), the archetypical endurance athlete, have electrocardiographic evidence of cardiac chamber enlargement and hypertrophy relative to sedentary captive gray wolves (n=20), as demonstrated by significant increases in QRS duration, QT interval, and QT interval corrected for heart rate, a tendency towards increased Q, R, and S wave voltages in all leads, and a significant decrease in heart rate. We conclude that exercise activity level and therefore lifestyle affects physiologic variables in wild animals. An immediate consequence of this finding is that physiologic measurements obtained from a captive wild-animal population with reduced exercise activity level may not accurately reflect the normal physiologic state for free-ranging members of the same species.

High prevalence of Mycobacterium tuberculosis mixed infection in the capital of moderate tuberculosis incidence country.

PubMed

Hajimiri, Elahe Sadat; Masoomi, Morteza; Ebrahimzadeh, Nayereh; Fateh, Abolfazl; Hadizadeh Tasbiti, Alireza; Rahimi Jamnani, Fatemeh; Bahrmand, Ahmad Reza; Mirsaeidi, Mehdi; Vaziri, Farzam; Siadat, Seyed Davar

2016-04-01

Recent studies using molecular epidemiological techniques have demonstrated mixed infection with multiple strains of Mycobacterium tuberculosis especially in countries with high tuberculosis (TB) burden. We aimed to determine the prevalence of mixed infection among patients with TB in the capital of Iran as a country with moderate incidence rate. Samples were collected randomly from January 2011 to December 2013 in Tehran, capital of Iran. A total of 75 M. tuberculosis isolates were genotyped by 24 loci mycobacterial interspersed repetitive unit-variable number tandem repeat typing (MIRU-VNTR) for screening the mixed infection. Twenty patients (20/75) were identified with mixed infection, and the estimated rate of mixed infection was 26.6%. Thirteen out of the 24 loci were able to detect the mixed infection in our study. Mixed infections occur at high prevalence among studied Iranian TB patients. Further research is inevitable to evaluate the association of mixed infection and disease progression and treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Amniotic fluid index predicts the relief of variable decelerations after amnioinfusion bolus.

PubMed

Spong, C Y; McKindsey, F; Ross, M G

1996-10-01

Our purpose was to determine whether intrapartum amniotic fluid index before amnioinfusion can be used to predict response to therapeutic amnioinfusion. Intrapartum patients (n = 85) with repetitive variable decelerations in fetal heart rate that necessitated amnioinfusion (10 ml/min for 60 minutes) underwent determination of amniotic fluid index before and after bolus amnioinfusion. The fetal heart tracing was scored (scorer blinded to amniotic fluid index values) for number and characteristics of variable decelerations before and 1 hour after initiation of amnioinfusion. The amnioinfusion was considered successful if it resulted in a decrease of > or = 50% in total number of variable decelerations or a decrease of > or = 50% in the rate of atypical or severe variable decelerations after administration of the bolus. Spontaneous vaginal births before completion of administration of the bolus (n = 18) were excluded from analysis. The probability of success of amnioinfusion in relation to amniotic fluid index was analyzed with the chi(2) test for progressive sequence. The mean amniotic fluid index before amnioinfusion was 6.2 +/- 3.3 cm. An amniotic fluid index of < or = 5 cm was present in 40% of patients (27/67), and an amniotic fluid index of < or = 8 cm was present in 72% of patients (48/67). The probability of success of amnioinfusion decreased with increasing amniotic fluid index before amnioinfusion (76% [16/21] when initial amniotic fluid index was 0 to 4 cm, 63% [17/27] when initial amniotic fluid index was 4 to 8 cm, 44% [7/16] when initial amniotic fluid index was 8 to 12 cm, and 33% [1/3] when initial amniotic fluid index was > 12 cm, p = 0.03). The incidence of nuchal cords or true umbilical cord knots increased in relation to amniotic fluid index before amnioinfusion. Amniotic fluid index before amnioinfusion can be used to predict the success of amnioinfusion for relief of variable decelerations in fetal heart rate. Failure of amnioinfusion at a high amniotic fluid index before amnioinfusion may be explained by the increased prevalence of nuchal cords or true knots in the umbilical cord.

Pure rotational CARS thermometry studies of low-temperature oxidation kinetics in air and ethene-air nanosecond pulse discharge plasmas

NASA Astrophysics Data System (ADS)

Zuzeek, Yvette; Choi, Inchul; Uddi, Mruthunjaya; Adamovich, Igor V.; Lempert, Walter R.

2010-03-01

Pure rotational CARS thermometry is used to study low-temperature plasma assisted fuel oxidation kinetics in a repetitive nanosecond pulse discharge in ethene-air at stoichiometric and fuel lean conditions at 40 Torr pressure. Air and fuel-air mixtures are excited by a burst of high-voltage nanosecond pulses (peak voltage, 20 kV; pulse duration, ~ 25 ns) at a 40 kHz pulse repetition rate and a burst repetition rate of 10 Hz. The number of pulses in the burst is varied from a few pulses to a few hundred pulses. The results are compared with the previously developed hydrocarbon-air plasma chemistry model, modified to incorporate non-empirical scaling of the nanosecond discharge pulse energy coupled to the plasma with number density, as well as one-dimensional conduction heat transfer. Experimental time-resolved temperature, determined as a function of the number of pulses in the burst, is found to agree well with the model predictions. The results demonstrate that the heating rate in fuel-air plasmas is much faster compared with air plasmas, primarily due to energy release in exothermic reactions of fuel with O atoms generated by the plasma. It is found that the initial heating rate in fuel-air plasmas is controlled by the rate of radical (primarily O atoms) generation and is nearly independent of the equivalence ratio. At long burst durations, the heating rate in lean fuel air-mixtures is significantly reduced when all fuel is oxidized.

A vacuum-sealed, gigawatt-class, repetitively pulsed high-power microwave source

NASA Astrophysics Data System (ADS)

Xun, Tao; Fan, Yu-wei; Yang, Han-wu; Zhang, Zi-cheng; Chen, Dong-qun; Zhang, Jian-de

2017-06-01

A compact L-band sealed-tube magnetically insulated transmission line oscillator (MILO) has been developed that does not require bulky external vacuum pump for repetitive operations. This device with a ceramic insulated vacuum interface, a carbon fiber array cathode, and non-evaporable getters has a base vacuum pressure in the low 10-6 Pa range. A dynamic 3-D Monte-Carlo model for the molecular flow movement and collision was setup for the MILO chamber. The pulse desorption, gas evolution, and pressure distribution were exactly simulated. In the 5 Hz repetition rate experiments, using a 600 kV diode voltage and 48 kA beam current, the average radiated microwave power for 25 shots is about 3.4 GW in 45 ns pulse duration. The maximum equilibrium pressure is below 4.0 × 10-2 Pa, and no pulse shortening limitations are observed during the repetitive test in the sealed-tube condition.

The Effects of Repetition on Children’s True and False Reports

PubMed Central

Evans, Angela D.; Brunet, Megan K.; Talwar, Victoria; Bala, Nicholas; Lindsay, Rod C.L.; Lee, Kang

2013-01-01

As children are often called upon to provide testimony in court proceedings, determining the veracity of their statements is an important issue. In the course of investigation by police and social workers, children are often repeatedly interviewed about their experiences, though the impact of this repetition on children’s true and false statements remains largely unexamined. The current study analysed semantic differences in children’s truthful and fabricated statements about an event they had or had not participated in. Results revealed that children’s truthful and fabricated reports differed in linguistic content, and that their language also varied with repetition. Discriminant analyses revealed that with repetition, children’s true and false reports became increasingly difficult to differentiate using linguistic markers, though true reports were consistently classified correctly at higher rates than false reports. The implications of these findings for legal procedures concerning child witnesses are discussed. PMID:24265592

Motor unit potential induced repetitive discharges (MIRDs): description of an unusual iterative discharge.

PubMed

So, Noel F; Rubin, Devon I; Jones, Lyell K; Litchy, William J; Sorenson, Eric J

2013-12-01

Repetitive discharges may be recorded during nerve conduction studies (NCS) or during needle electromyography in a muscle at rest. Repetitive discharges that occur during voluntary activation and are time-locked to voluntary motor unit potentials (MUP) have not been described. Retrospective review of motor unit potential induced repetitive discharges (MIRDs) identified in the EMG laboratory. Characteristics of each MIRD, patient demographics, other EMG findings in the same muscle, and electrophysiological diagnosis were analyzed. MIRDs were observed in 15 patients. The morphology and number of spikes and duration of MIRDs varied. The discharges fired at rates of 50-200 Hz. All but 2 patients had EMG findings of a chronic neurogenic disorder. MIRDs are rare iterative discharges time-locked to a voluntary MUP. The pathophysiology of MIRDs is unclear, but their presence may indicate a chronic neurogenic process. Copyright © 2013 Wiley Periodicals, Inc.

Identification of anaerobic threshold by analysis of heart rate variability during discontinuous dynamic and resistance exercise protocols in healthy older men.

PubMed

Simões, Rodrigo Polaquini; Castello-Simões, Viviane; Mendes, Renata Gonçalves; Archiza, Bruno; Dos Santos, Daniel Augusto; Bonjorno, José Carlos; de Oliveira, Claudio Ricardo; Catai, Aparecida Maria; Arena, Ross; Borghi-Silva, Audrey

2014-03-01

The purposes of this study were to determine anaerobic threshold (AT) during discontinuous dynamic and resistive exercise protocols by analysing of heart rate variability (HRV) and blood lactate (BL) in healthy elderly subjects and compare the cardiovascular, metabolic and autonomic variables obtained from these two forms of exercise. Fourteen elderly (70 ± 4 years) apparently healthy males underwent the following tests: (i) incremental ramp test on cycle ergometer, (ii) one repetition maximum (1RM) leg press at 45°, (iii) a discontinuous exercise test on a cycle ergometer (DET-C) protocol and (iv) a resistance exercise leg press (DET-L) protocol. Heart rate, blood pressure and BL were obtained during each increment of exercise intensity. No significant differences (P>0·05) were found between methods of AT determination (BL and HRV) nor the relative intensity corresponding to AT (30% of maximum intensity) between the types of exercise (DET-C and DET-L). Furthermore, no significant differences (P>0·05) were found between the DET-C and DET-L in relation to HRV, however, the DET-L provided higher values of systolic blood pressure and BL (P<0·05) from the intensity corresponding to AT. We conclude that HRV was effective in determination of AT, and the parasympathetic modulation responses obtained during dynamic and resistive exercise protocols were similar when compared at the same relative intensity. However, DET-L resulted in higher values of blood pressure and BL at workloads beyond AT. © 2013 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd.

Repeated head trauma is associated with smaller thalamic volumes and slower processing speed: the Professional Fighters’ Brain Health Study

PubMed Central

Bernick, Charles; Banks, Sarah J; Shin, Wanyong; Obuchowski, Nancy; Butler, Sam; Noback, Michael; Phillips, Michael; Lowe, Mark; Jones, Stephen; Modic, Michael

2015-01-01

Objectives Cumulative head trauma may alter brain structure and function. We explored the relationship between exposure variables, cognition and MRI brain structural measures in a cohort of professional combatants. Methods 224 fighters (131 mixed martial arts fighters and 93 boxers) participating in the Professional Fighters Brain Health Study, a longitudinal cohort study of licensed professional combatants, were recruited, as were 22 controls. Each participant underwent computerised cognitive testing and volumetric brain MRI. Fighting history including years of fighting and fights per year was obtained from self-report and published records. Statistical analyses of the baseline evaluations were applied cross-sectionally to determine the relationship between fight exposure variables and volumes of the hippocampus, amygdala, thalamus, caudate, putamen. Moreover, the relationship between exposure and brain volumes with cognitive function was assessed. Results Increasing exposure to repetitive head trauma measured by number of professional fights, years of fighting, or a Fight Exposure Score (FES) was associated with lower brain volumes, particularly the thalamus and caudate. In addition, speed of processing decreased with decreased thalamic volumes and with increasing fight exposure. Higher scores on a FES used to reflect exposure to repetitive head trauma were associated with greater likelihood of having cognitive impairment. Conclusions Greater exposure to repetitive head trauma is associated with lower brain volumes and lower processing speed in active professional fighters. PMID:25633832

Heart-rate pulse-shift detector

NASA Technical Reports Server (NTRS)

Anderson, M.

1974-01-01

Detector circuit accurately separates and counts phase-shift pulses over wide range of basic pulse-rate frequency, and also provides reasonable representation of full repetitive EKG waveform. Single telemeter implanted in small animal monitors not only body temperature but also animal movement and heart rate.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Stationary force produced by an optical pulsating discharge in a laser engine model

NASA Astrophysics Data System (ADS)

Grachev, Gennadii N.; Tishchenko, V. N.; Apollonov, V. V.; Gulidov, A. I.; Smirnov, A. L.; Sobolev, A. V.; Zimin, M. I.

2007-07-01

An optical pulsating discharge produced by repetitively pulses laser radiation (with a pulse repetition rate of up to 100 kHz) is studied in a cylindrical tube simulating the reflector of a laser engine. The pressure of shock waves and the propulsion produced by them are measured. The discharge produced the stationary propulsion ~1 N kW-1.

Beauty is in the belief of the beholder: cognitive influences on the neural response to facial attractiveness.

PubMed

Thiruchselvam, Ravi; Harper, Jessica; Homer, Abigail L

2016-12-01

Judgments of facial attractiveness are central to decision-making in various domains, but little is known about the extent to which they are malleable. In this study, we used EEG/ERP methods to examine two novel influences on neural and subjective responses to facial attractiveness: an observer's expectation and repetition. In each trial of our task, participants viewed either an ordinary or attractive face. To alter expectations, the faces were preceded by a peer-rating that ostensibly reflected the overall attractiveness value assigned to that face by other individuals. To examine the impact of repetition, trials were presented twice throughout the experimental session. Results showed that participants' expectations about a person's attractiveness level powerfully altered both the neural response (i.e. the late positive potential; LPP) and self-reported attractiveness ratings. Intriguingly, repetition enhanced both the LPP and self-reported attractiveness as well. Exploratory analyses further suggested that both observer expectation and repetition modulated early neural responses (i.e. the early posterior negativity; EPN) elicited by facial attractiveness. Collectively, these results highlight novel influences on a core social judgment that underlies individuals' affective lives. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

Validity of Various Methods for Determining Velocity, Force, and Power in the Back Squat.

PubMed

Banyard, Harry G; Nosaka, Ken; Sato, Kimitake; Haff, G Gregory

2017-10-01

To examine the validity of 2 kinematic systems for assessing mean velocity (MV), peak velocity (PV), mean force (MF), peak force (PF), mean power (MP), and peak power (PP) during the full-depth free-weight back squat performed with maximal concentric effort. Ten strength-trained men (26.1 ± 3.0 y, 1.81 ± 0.07 m, 82.0 ± 10.6 kg) performed three 1-repetition-maximum (1RM) trials on 3 separate days, encompassing lifts performed at 6 relative intensities including 20%, 40%, 60%, 80%, 90%, and 100% of 1RM. Each repetition was simultaneously recorded by a PUSH band and commercial linear position transducer (LPT) (GymAware [GYM]) and compared with measurements collected by a laboratory-based testing device consisting of 4 LPTs and a force plate. Trials 2 and 3 were used for validity analyses. Combining all 120 repetitions indicated that the GYM was highly valid for assessing all criterion variables while the PUSH was only highly valid for estimations of PF (r = .94, CV = 5.4%, ES = 0.28, SEE = 135.5 N). At each relative intensity, the GYM was highly valid for assessing all criterion variables except for PP at 20% (ES = 0.81) and 40% (ES = 0.67) of 1RM. Moreover, the PUSH was only able to accurately estimate PF across all relative intensities (r = .92-.98, CV = 4.0-8.3%, ES = 0.04-0.26, SEE = 79.8-213.1 N). PUSH accuracy for determining MV, PV, MF, MP, and PP across all 6 relative intensities was questionable for the back squat, yet the GYM was highly valid at assessing all criterion variables, with some caution given to estimations of MP and PP performed at lighter loads.

Age differences in coupling of intraindividual variability in mnemonic strategies and practice-related associative recall improvements.

PubMed

Hertzog, Christopher; Lövdén, Martin; Lindenberger, Ulman; Schmiedek, Florian

2017-09-01

The importance of encoding strategies for associative recall is well established, but there have been no studies of aging and intraindividual variability (IAV) in strategy use during extended practice. We observed strategy use and cued-recall test performance over 101 days of practice in 101 younger adults (M = 25.6 years) and 103 older adults (M = 71.3 years) sandwiched by a pretest and posttest battery including an associative recall test. Each practice session included 2 lists of 12 number-noun paired-associate (PA) items (e.g., 23-DOGS), presented for brief exposures titrated to maintain below-ceiling performance throughout practice. Participants reported strategy use (e.g., rote repetition, imagery) after each test. Substantial IAV in strategy use was detected that was coupled with performance; lists studied with normatively effective strategies (e.g., imagery) generated higher PA recall than lists studied with less effective strategies (e.g., rote repetition). In comparison to younger adults, older adults' practice (a) relied more on repetition and less on effective strategies, (b) showed lower levels of IAV in effective strategy use, and (c) had lower within-person strategy-recall coupling, especially late in practice. Individual differences in pretest-posttest gains in PA recall were predicted by average level of effective strategy use in young adults but by strategy-recall coupling in older adults. Results are consistent with the hypothesis that experiencing variability in strategic outcomes during practice helps hone the effectiveness of strategic encoding behavior, and that older adults' reduced degree of pretest-posttest gains is influenced by lower likelihood of using and optimizing effective strategies through practice. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Further characterization of repetitive behavior in C58 mice: developmental trajectory and effects of environmental enrichment.

PubMed

Muehlmann, A M; Edington, G; Mihalik, A C; Buchwald, Z; Koppuzha, D; Korah, M; Lewis, M H

2012-12-01

Aberrant repetitive behaviors are commonly observed in a variety of neurodevelopmental, neurological, and neuropsychiatric disorders. Little is known about the specific neurobiological mechanisms that underlie such behaviors, however, and effective treatments are lacking. Valid animal models can aid substantially in identifying pathophysiological factors mediating aberrant repetitive behavior and aid in treatment development. The C58 inbred mouse strain is a particularly promising model, and we have further characterized its repetitive behavior phenotype. Compared to C57BL/6 mice, C58 mice exhibit high rates of spontaneous hindlimb jumping and backward somersaulting reaching adult frequencies by 5 weeks post-weaning and adult temporal organization by 2 weeks post-weaning. The development of repetitive behavior in C58 mice was markedly attenuated by rearing these mice in larger, more complex environments. In addition to characterizing repetitive motor behavior, we also assessed related forms of inflexible behavior that reflect restricted and perseverative responding. Contrary to our hypothesis, C58 mice did not exhibit increased marble burying nor did they display reduced exploratory behavior in the holeboard task. The C58 strain appears to be a very useful model for the repetitive motor behavior characteristic of a number of clinical disorders. As an inbred mouse strain, studies using the C58 model can take full advantage of the tool kit of modern genetics and molecular neuroscience. This technical advantage makes the model a compelling choice for use in studies designed to elucidate the etiology and pathophysiology of aberrant repetitive behavior. Such findings should, in turn, translate into effective new treatments. Published by Elsevier B.V.

100-kHz shot-to-shot broadband data acquisition for high-repetition-rate pump-probe spectroscopy.

PubMed

Kanal, Florian; Keiber, Sabine; Eck, Reiner; Brixner, Tobias

2014-07-14

Shot-to-shot broadband detection is common in ultrafast pump-probe spectroscopy. Taking advantage of the intensity correlation of subsequent laser pulses improves the signal-to-noise ratio. Finite data readout times of CCD chips in the employed spectrometer and the maximum available speed of mechanical pump-beam choppers typically limit this approach to lasers with repetition rates of a few kHz. For high-repetition (≥ 100 kHz) systems, one typically averages over a larger number of laser shots leading to inferior signal-to-noise ratios or longer measurement times. Here we demonstrate broadband shot-to-shot detection in transient absorption spectroscopy with a 100-kHz femtosecond laser system. This is made possible using a home-built high-speed chopper with external laser synchronization and a fast CCD line camera. Shot-to-shot detection can reduce the data acquisition time by two orders of magnitude compared to few-kHz lasers while keeping the same signal-to-noise ratio.

Picosecond laser system with 30-W average power via cavity dumping and amplifying

NASA Astrophysics Data System (ADS)

Fu, J.; Pang, Q. S.; Chang, L.; Bai, Z. A.; Ai, Q. K.; Chen, L. Y.; Chen, M.; Li, G.; Ma, Y. F.; Fan, Z. W.; Niu, G.; Yu, J.; Liu, Y.; Zhang, X.; Kang, W. Y.; He, K.

2011-06-01

We present a picosecond laser system with high energy by technologies of cavity dumping and amplifying. Firstly, pulses with 10 ps and ˜520 nJ were obtained by cavity-dumped mode-locked laser at 10 kHz repetition rate. Secondly those pulses were seeded into a side-pumped regenerative amplifier (RA). Then pulses output from the regenerative amplifier were amplified by two four-pass post amplifiers. From the laser system pulses with an average power of 30 W corresponding to 3 mJ pulse energy were achieved with the pulse-width of 25.4 ps at repetition rate of 10 kHz.

High power high repetition rate VCSEL array side-pumped pulsed blue laser

NASA Astrophysics Data System (ADS)

van Leeuwen, Robert; Zhao, Pu; Chen, Tong; Xu, Bing; Watkins, Laurence; Seurin, Jean-Francois; Xu, Guoyang; Miglo, Alexander; Wang, Qing; Ghosh, Chuni

2013-03-01

High power, kW-class, 808 nm pump modules based on the vertical-cavity surface-emitting laser (VCSEL) technology were developed for side-pumping of solid-state lasers. Two 1.2 kW VCSEL pump modules were implemented in a dual side-pumped Q-switched Nd:YAG laser operating at 946 nm. The laser output was frequency doubled in a BBO crystal to produce pulsed blue light. With 125 μs pump pulses at a 300 Hz repetition rate 6.1 W QCW 946 nm laser power was produced. The laser power was limited by thermal lensing in the Nd:YAG rod.

Application of the Repetitions in Reserve-Based Rating of Perceived Exertion Scale for Resistance Training

PubMed Central

Cronin, John; Storey, Adam; Zourdos, Michael C.

2016-01-01

ABSTRACT RATINGS OF PERCEIVED EXERTION ARE A VALID METHOD OF ESTIMATING THE INTENSITY OF A RESISTANCE TRAINING EXERCISE OR SESSION. SCORES ARE GIVEN AFTER COMPLETION OF AN EXERCISE OR TRAINING SESSION FOR THE PURPOSES OF ATHLETE MONITORING. HOWEVER, A NEWLY DEVELOPED SCALE BASED ON HOW MANY REPETITIONS ARE REMAINING AT THE COMPLETION OF A SET MAY BE A MORE PRECISE TOOL. THIS APPROACH ADJUSTS LOADS AUTOMATICALLY TO MATCH ATHLETE CAPABILITIES ON A SET-TO-SET BASIS AND MAY MORE ACCURATELY GAUGE INTENSITY AT NEAR-LIMIT LOADS. THIS ARTICLE OUTLINES HOW TO INCORPORATE THIS NOVEL SCALE INTO A TRAINING PLAN. PMID:27531969

The Multidisk Diode-Pumped High Power Yb:YAG Laser Amplifier of High-Intensity Laser System with 1 kHz Repetition Rate

NASA Astrophysics Data System (ADS)

Kuptsov, G. V.; Petrov, V. V.; Petrov, V. A.; Laptev, A. V.; Kirpichnikov, A. V.; Pestryakov, E. V.

2018-04-01

The source of instabilities in the multidisk diode-pumped high power Yb:YAG laser amplifier with cryogenic closed-loop cooling in the laser amplification channel of the high-intensity laser system with 1 kHz repetition rate was determined. Dissected copper mounts were designed and used to suppress instabilities and to achieve repeatability of the system. The equilibrium temperature dependency of the active elements on average power was measured. The seed laser for the multidisk amplifier was numerically simulated and designed to allow one to increase pulses output energy after the amplifier up to 500 mJ.