Material conformity and bactericidal properties of high-frequency-pulse-modulated and low-frequency-pulse-excited plasmas

To determine the possibility to deconvolve measured BOLD responses to neuronal signals, the rat perforant pathway was electrically stimulated with 10 related stimulation protocols. All stimulation protocols were composed of low-frequency pulse sequences with superimposed high-frequency pulse bursts. Because high-frequency pulse bursts trigger only one synchronized spiking of granular cells, variations of the stimulation protocol were used: (a) to keep the spiking activity similar during the presentation of different numbers of pulses, (b) to apply identical numbers of pulses to induce different amounts of spiking activity, and (c) to concurrently vary the number of applied electrical pulses and resultant spiking activity. When complex pulse sequences enter the hippocampus, an unspecific default-like BOLD response is first generated, which relates neither to the number of incoming pulses nor to the induced spiking activity. Only during subsequent stimulations does the initial unspecific response adjust to a more adequate response, which in turn either strongly related to spiking activity when low-frequency pulses were applied or depended on the incoming activity when high-frequency pulse bursts were presented. Thus, only the development of BOLD responses during repetitive stimulations can predict the underlying neuronal activity and deconvolution analysis should not be performed during an initial stimulation period.

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Fatigue of Paralyzed and Control Thenar Muscles Induced by Variable or Constant Frequency Stimulation

Journal of Neurophysiology ◽

10.1152/jn.01002.2002 ◽

2003 ◽

Vol 89 (4) ◽

pp. 2055-2064 ◽

Cited By ~ 50

Author(s):

Christine K. Thomas ◽

Lisa Griffin ◽

Sharlene Godfrey ◽

Edith Ribot-Ciscar ◽

Jane E. Butler

Keyword(s):

Spinal Cord ◽

High Frequency ◽

Low Frequency ◽

Constant Frequency ◽

Time Integral ◽

Frequency Stimulation ◽

Force Time ◽

And Control ◽

Frequency Pulse ◽

Force Time Integral

Muscles paralyzed by chronic (>1 yr) spinal cord injury fatigue readily. Our aim was to evaluate whether the fatigability of paralyzed thenar muscles ( n = 10) could be reduced by the repeated delivery of variable versus constant frequency pulse trains. Fatigue was induced in four ways. Intermittent supramaximal median nerve stimulation (300-ms-duration trains) was delivered at 1) constant high frequency (13 pulses at 40 Hz each second for 2 min); 2) variable high frequency (each second for 2 min). The first two intervals of each variable frequency train were 5 and 20 ms. The remaining pulses were evenly distributed in time across 275 ms. The number of pulses varied for each subject such that the force time integral in the unfatigued state matched that evoked by a constant 40-Hz train; 3) constant low frequency (7 pulses at 20 Hz each second for 4 min); and 4) variable low frequency (each second for 4 min). The pulse pattern was the same as that for variable high frequency except that the force-time integral was matched to that produced by the constant low-frequency stimulation. These same experiments were performed on the thenar muscles of five able-bodied control subjects. The variable high-frequency trains used to fatigue paralyzed and control muscles had an average (± SE) of 12 ± 2 and 10 ± 1 pulses, respectively. Variable low-frequency trains had 7 ± 1 and 6 ± 1 pulses, respectively. Significant mean force declines of comparable magnitude (to 20–25% initial fatigue force or to 13–21% initial 50 Hz force) were seen in paralyzed muscles with all four stimulation protocols. The force reductions in paralyzed muscles were always accompanied by significant increases in half-relaxation time and decreases in force-time integral, irrespective of the stimulation protocol. Significant force decreases also occurred in control muscles during each fatigue test. Again, these force declines were similar whether constant or variable pulse patterns were used at high or low frequencies (to 40–60% initial fatigue force or to 29–36% initial 50 Hz force). The force reductions in control muscles were significantly less than those seen in paralyzed muscles, except when constant high-frequency stimulation was used. The variations in stimulation frequency, pulse pattern, and pulse number used in this study therefore had little influence on thenar muscle fatigue in control subjects or in spinal cord–injured subjects with chronic paralysis.

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ADDENDUM TO “STUDIES OF ELASTIC WAVE ATTENUATION IN POROUS MEDIA” BY M. R. J. WYLLIE, G. H. F. GARDNER, AND A. R. GREGORY (GEOPHYSICS, OCTOBER, 1962, PP. 569–589)

Geophysics ◽

10.1190/1.1439306 ◽

1963 ◽

Vol 28 (6) ◽

pp. 1074-1074 ◽

Cited By ~ 7

Author(s):

M. R. J. Wyllie ◽

G. H. F. Gardner ◽

A. R. Gregory

Keyword(s):

High Frequency ◽

Critical Angle ◽

Wave Attenuation ◽

Low Frequency ◽

Shear Velocity ◽

Confining Pressure ◽

Biot’S Theory ◽

Biot's Theory ◽

Angle Method ◽

Frequency Pulse

In the paper published last year we noted that the shear velocity through liquid‐saturated rocks often appeared to exceed the shear velocity through the same rocks when dry. Our results were based on measurements made by the critical‐angle method on rocks subjected to heavy confining pressure. We felt constrained to observe that, if shear velocities through liquid‐saturated rocks were higher than through their dry counterparts, the applicability of Biot’s theory to any but low‐frequency resonating systems was open to question. Because Biot’s theory will be of maximum use only if it can be applied to systems in which velocities are measured by high‐frequency pulse techniques, our warning diminished the practical value of our other results.

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Design and Implementation of a Dimmable LED Driver with Low-Frequency PWM Control

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.2538 ◽

2013 ◽

Vol 284-287 ◽

pp. 2538-2542

Author(s):

Hung Liang Cheng ◽

Chun An Cheng ◽

Chao Shun Chen ◽

Kuan Lung Huang

Keyword(s):

High Frequency ◽

High Efficiency ◽

Low Frequency ◽

Buck Converter ◽

Duty Ratio ◽

Buck Converters ◽

Resonant Converter ◽

Switching Loss ◽

Led Driver ◽

Frequency Pulse

This paper proposes a high-efficiency dimmable LED driver for light emitting diodes (LED). The developed LED driver consists of a full-bridge resonant converter and six buck converters. The function of the full-bridge resonant converter is to obtain a smooth dc-link voltage for the buck converters by phase-shift modulation (PSM) while that of the six buck converters is to drive six LED modules, respectively. The gate voltage of the active switch of each buck converter is a combination of high-frequency and low-frequency pulses. The duty ratio of the high-frequency pulse controls the LED voltage and thereby, controls the amplitude of LED current. LEDs are dimmed by low-frequency pulse-width modulation (PWM) to vary the average current flowing through LED. Circuit equations are derived and circuit parameters are designed. High circuit efficiency is ensured by operating the active switches at zero-voltage switching-on to reduce the switching loss. Finally, a prototype circuit was built to verify the accuracy and feasibility of the proposed LED driver.

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Simulations of high-resolution images of amorphous silicon films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010014419x ◽

1986 ◽

Vol 44 ◽

pp. 544-545

Author(s):

G. Y. Fan ◽

J. M. Cowley

Keyword(s):

Electron Microscope ◽

High Frequency ◽

Fourier Transformation ◽

Amorphous Materials ◽

Low Frequency ◽

Chromatic Aberration ◽

Structure Information ◽

Frequency Components ◽

High Resolution Images ◽

Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

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SEM image sharpness analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163174 ◽

1996 ◽

Vol 54 ◽

pp. 142-143

Author(s):

M. T. Postek ◽

A. E. Vladar

Keyword(s):

High Frequency ◽

Low Frequency ◽

Quantitative Information ◽

Primary Electron ◽

Image Sharpness ◽

Critical Dimensions ◽

Sem Image ◽

Frequency Changes ◽

Electron Microscopes ◽

Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

American Journal of Audiology ◽

10.1044/1059-0889.0104.52 ◽

1992 ◽

Vol 1 (4) ◽

pp. 52-55 ◽

Cited By ~ 4

Author(s):

Gail L. MacLean ◽

Andrew Stuart ◽

Robert Stenstrom

Keyword(s):

High Frequency ◽

Sound Pressure ◽

Low Frequency ◽

Test System ◽

Output Frequency ◽

Frequency Effects ◽

Adult Men ◽

Frequency Responses ◽

Significant Difference ◽

Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

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Evaluation of Special Hearing Aids for Deaf Children

Journal of Speech and Hearing Disorders ◽

10.1044/jshd.3604.527 ◽

1971 ◽

Vol 36 (4) ◽

pp. 527-537 ◽

Cited By ~ 1

Author(s):

Norman P. Erber

Keyword(s):

Hearing Aids ◽

High Frequency ◽

Hearing Aid ◽

Low Frequency ◽

Acoustic Stimulation ◽

Deaf Children ◽

Frequency Range ◽

Frequency Limit ◽

Unpublished Studies ◽

Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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Efeitos do Método Pilates sobre a variabilidade da frequência cardíaca, flexibilidade e variáveis antropométricas em indivíduos sedentários

Fisioterapia Brasil ◽

10.33233/fb.v17i1.26 ◽

2016 ◽

Vol 17 (1) ◽

pp. 66

Author(s):

Maria Lina Silva Leite

Keyword(s):

High Frequency ◽

Low Frequency

O objetivo deste estudo foi avaliar os efeitos do Método Pilates sobre a variabilidade da frequência cardíaca, na flexibilidade e nas variáveis antropométricas em indivíduos sedentários. O presente estudo contou com 14 voluntárias do sexo feminino, na faixa etária entre 40 e 55 anos, que realizaram 20 sessões de exercícios do Método Pilates, duas vezes por semana, com duração de 45 minutos cada sessão, dividida em três fases: repouso, exercício e recuperação. As variáveis estudadas foram: os dados antropométricos, flexibilidade avaliada utilizando o teste de sentar-e-alcançar com o Banco de Wells, e intervalos R-R usando um cardiotacômetro. O processamento dos sinais da frequência cardíaca foi efetuado em ambiente MatLab 6.1®, utilizando a TWC. Os dados coletados foram submetidos ao teste de normalidade de Shapiro Wilk e foi utilizado o teste de Wilcoxon e Anova One Way (α = 0,05). Nos resultados, observou-se que não houve diferenças significativas entre os valores antropométricos e de frequência cardíaca, porém houve aumento da flexibilidade com o treinamento. Comparando a primeira e a vigésima sessão com relação aos parâmetros low frequency (LF), high frequency (HF), e relação LF/HF, não houve diferença na fase de repouso e foram constatadas diferenças significativas de LF (p = 0,04) e HF (p = 0,04) na fase de exercício e diferença significativa de LF/HF (p = 0,05) na fase de recuperação. Comparando os parâmetros nos períodos de repouso, exercícios e recuperação durante a primeira sessão e durante a vigésima sessão, não houve diferença significativa nos parâmetros LF, HF e LF/HF. Pode-se concluir que, em relação à flexibilidade, foi observada uma melhora significativa, enquanto a análise da frequência cardíaca caracterizou a intensidade do exercício de 50% da capacidade funcional das voluntárias. Em relação aos parâmetros LF, HF e LF/HF foram observados um aumento da variabilidade da frequência cardíaca, provavelmente produto da atividade do Método Pilates. A Transformada Wavelet (TWC) mostrou-se um Método adequado para as análises da variabilidade da frequência cardíaca.Palavras-chave: frequência cardíaca, Transformada Wavelet, Pilates.

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Dynamics of the processes in metal machining

Nonlinear Analysis Modelling and Control ◽

10.15388/na.1998.2.0.15295 ◽

1998 ◽

Vol 2 ◽

pp. 115-122

Author(s):

Donatas Švitra ◽

Jolanta Janutėnienė

Keyword(s):

High Frequency ◽

Machine Tools ◽

Metal Cutting ◽

Cutting Tool ◽

Low Frequency ◽

Metal Cutting Machine ◽

Cutting Machine ◽

Metal Machining

In the practice of processing of metals by cutting it is necessary to overcome the vibration of the cutting tool, the processed detail and units of the machine tool. These vibrations in many cases are an obstacle to increase the productivity and quality of treatment of details on metal-cutting machine tools. Vibration at cutting of metals is a very diverse phenomenon due to both it’s nature and the form of oscillatory motion. The most general classification of vibrations at cutting is a division them into forced vibration and autovibrations. The most difficult to remove and poorly investigated are the autovibrations, i.e. vibrations arising at the absence of external periodic forces. The autovibrations, stipulated by the process of cutting on metalcutting machine are of two types: the low-frequency autovibrations and high-frequency autovibrations. When the low-frequency autovibration there appear, the cutting process ought to be terminated and the cause of the vibrations eliminated. Otherwise, there is a danger of a break of both machine and tool. In the case of high-frequency vibration the machine operates apparently quiently, but the processed surface feature small-sized roughness. The frequency of autovibrations can reach 5000 Hz and more.

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