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Pulse Parameters (pulse + parameter)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Effect of pulsing in low-level light therapy,

LASERS IN SURGERY AND MEDICINE, Issue 6 2010
Javad T. Hashmi MD
Abstract Background and Objective Low level light (or laser) therapy (LLLT) is a rapidly growing modality used in physical therapy, chiropractic, sports medicine and increasingly in mainstream medicine. LLLT is used to increase wound healing and tissue regeneration, to relieve pain and inflammation, to prevent tissue death, to mitigate degeneration in many neurological indications. While some agreement has emerged on the best wavelengths of light and a range of acceptable dosages to be used (irradiance and fluence), there is no agreement on whether continuous wave or pulsed light is best and on what factors govern the pulse parameters to be chosen. Study Design/Materials and Methods The published peer-reviewed literature was reviewed between 1970 and 2010. Results The basic molecular and cellular mechanisms of LLLT are discussed. The type of pulsed light sources available and the parameters that govern their pulse structure are outlined. Studies that have compared continuous wave and pulsed light in both animals and patients are reviewed. Frequencies used in other pulsed modalities used in physical therapy and biomedicine are compared to those used in LLLT. Conclusion There is some evidence that pulsed light does have effects that are different from those of continuous wave light. However further work is needed to define these effects for different disease conditions and pulse structures. Lasers Surg. Med. 42:450,466, 2010. © 2010 Wiley,Liss, Inc. [source]

Spin-echo MRI using ,/2 and , hyperbolic secant pulses,

MAGNETIC RESONANCE IN MEDICINE, Issue 1 2009
Jang-Yeon Park
Abstract Frequency-modulated (FM) pulses have practical advantages for spin-echo experiments, such as the ability to produce a broadband , rotation, with an inhomogeneous radiofrequency (RF) field. However, such use leads to a nonlinear phase of the transverse magnetization, which is why FM pulses like the hyperbolic secant (HS) pulse are not commonly used for multislice spin-echo magnetic resonance imaging (MRI). Here, a general theory and methods are described for conventional spin-echo imaging using a , HS pulse for refocusing. Phase profiles produced by the HS pulse are analytically described. The analysis is extended to yield the specific relationships between pulse parameters and gradients, which must be satisfied to compensate the nonlinear phase variation produced with a spin-echo sequence composed of ,/2 and , HS pulses (the ,/2 HS , , HS sequence). The latter offers advantages for multislice spin-echo MRI, including excellent slice-selection and partial compensation for RF inhomogeneity. Furthermore, it can be implemented with a shorter echo time and lower power deposition than a previously described method using a pair of , HS pulses. Magn Reson Med 61:175,187, 2009. © 2008 Wiley-Liss, Inc. [source]

Impedance measurements on oxide films on aluminium obtained by pulsed tensions

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 1 2003
K. Belmokre
Anodisation; Elektrochemische Impedanzspektroskopie (EIS); pulsierende Spannung; Alterung von Oxidfilmen Abstract We have performed this study on oxide films sealed or not in boiling water. The films are first obtained on type 1050 A aluminium substrat by pulsed tensions anodizing technique, in a sulfuric acid solution. Afterwards the, Electrochemical Impedance Spectroscopy (EIS) is employed to appreciate the films behaviour in a neutral solution of 3.5% K2SO4, in which the interface processes interest only the ageing phenomenon of the oxide films and not their corrosion. We have also attempted a correlation between pulse parameters of anodization and the electrical parameters characterizing these films. The sealing influence on ageing has been studied as well. For all films, ageing is appreciated using impedance diagrams evolution versus time. The results show: , the existence of two capacitive loops confirming the presence of two oxide layers characteristic of oxide films obtained in a sulfuric acid medium. The first loop, at high frequencies, is related to the external porous layer and the second one, at lower freqencies, is related to the internal barrier layer. , the thickness of the barrier layer varies between 25 and 40 nm in relation with the electrical pulse parameters. , the sealing acts favorably against anodic oxide films ageing. Impedanzmessungen an durch pulsierende Spannung erzeugten Oxidfilmen auf Aluminium Die vorliegenden Untersuchungen wurden an versiegelten und nicht versiegelten Oxidfilmen in kochendem Wasser durchgeführt. Die Filme wurden zuerst auf Aluminiumsubstrat des Typs 1050A durch anodische Technik mit pulsierender Spannung in einer Schwefelsäurelösung erzeugt. Anschließend wurde die elektrochemische Impedanzspektroskopie eingesetzt, um das Filmverhalten in einer neutralen 3,5% K2SO4 -Lösung zu beurteilen, wobei bezüglich der Grenzflächenprozesse nur das Alterungsphänomen der Oxidfilme und nicht ihr Korrosionsverhalten interessierte. Es wurde versucht, eine Korrelation zwischen den Pulsparametern der Anodisierung und den elektrischen Parametern, die diese Filme charakterisieren, zu finden. Ebenfalls wurde der Versiegelungseinfluss auf die Alterung untersucht. Für alle Filme wurde die Alterung mit Hilfe der Entwicklung von Impedanzdiagrammen über die Zeit beurteilt. Die Ergebnisse zeigen: , die Existenz von zwei kapazitiven Schleifen, die die Anwesenheit von zwei Oxidschichten bestätigen, was charakteristisch ist für Oxidfilme, die in einer Schwefelsäurelösung erzeugt wurden. Die erste Schleife, bei hohen Frequenzen, bezieht sich auf die äußere poröse Schicht und die zweite, bei niedrigeren Frequenzen, bezieht sich auf die innere Barriereschicht , die Dicke der Barriereschicht variiert zwischen 25 und 40 nm, abhängig von den elektrischen Pulsparametern , die Versiegelung wirkt günstig gegenüber der Alterung des anodischen Oxidfilms. [source]