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Pulse Width (pulse + width)
Kinds of Pulse Width Selected AbstractsPhotoepilation Results of Axillary Hair in Dark-Skinned Patients by IPL: A Comparison Between Different Wavelength and Pulse WidthDERMATOLOGIC SURGERY, Issue 2 2006JONG HEE LEE MD BACKGROUND Recently, intense pulsed light (IPL) sources have been shown to provide long-term hair removal. OBJECTIVE This study examined the photoepilatory effects of different wavelengths and pulse width application in the same device and compared their efficiencies in Asian skin. METHODS Twenty-eight Korean women were treated using HR (600,950 nm filter) and 27 using HR-D (645,950 nm filter) in the axillar area. Four treatments were carried out at intervals of 4 to 6 weeks; follow-ups were conducted 8 months after the last treatment. Mean energy settings were 14.9±2.0 J/cm2 for HR and 17.1±0.6 J/cm2 for HR-D. Longer pulse widths were applied in case of HR-D treatment. Hair counts and photographic evaluation of skin sites were made at baseline and at the last follow-up. Final overall evaluations were performed by patients and clinicians. RESULTS Average clearances of 52.8% and 83.4% were achieved by HR and HR-D, respectively. No significant adverse effects were reported after HR-D treatment. One case each of hypopigmentation and hyperpigmentation was reported for HR. CONCLUSION An IPL source by removing 45 nm of the emitted spectra and applying longer pulse width was found to provide a safer and more effective means of photoepilation in Asian patients. [source] The Effects of Variable Pulse Width of Er:YAG Laser on Facial SkinDERMATOLOGIC SURGERY, Issue 4 2001Khalil A. Khatri MD Background. The use of CO2 and Er:YAG lasers for resurfacing has increased significantly in the past few years. Er:YAG laser causes pinpoint bleeding during and after treatment with a typical pulse width of 250 ,sec. A longer pulse of Er:YAG laser can potentially coagulate dermal blood vessels and increase the residual thermal damage (RTD). Objective. To evaluate the effects of various pulse durations of Er:YAG laser on the depth of RTD and bleeding. Methods. The preauricular skin of a volunteer was exposed to Er:YAG laser at 250-, 350-, and 700-,sec pulse durations, with a fluence of 5 J/cm2. The number of passes varied between 6 and 16. The treated skin was excised and a histologic evaluation was done. Results. The maximum depth of RTD was 50 ,m and there was decreased bleeding with a 700-,sec pulse duration. Conclusion. The increased pulse duration of Er:YAG laser of 700 ,s does not increase the maximum reported RTD and therefore would not change the recovery time and may have a beneficial effect on hemostasis. [source] Photoepilation Results of Axillary Hair in Dark-Skinned Patients by IPL: A Comparison Between Different Wavelength and Pulse WidthDERMATOLOGIC SURGERY, Issue 2 2006JONG HEE LEE MD BACKGROUND Recently, intense pulsed light (IPL) sources have been shown to provide long-term hair removal. OBJECTIVE This study examined the photoepilatory effects of different wavelengths and pulse width application in the same device and compared their efficiencies in Asian skin. METHODS Twenty-eight Korean women were treated using HR (600,950 nm filter) and 27 using HR-D (645,950 nm filter) in the axillar area. Four treatments were carried out at intervals of 4 to 6 weeks; follow-ups were conducted 8 months after the last treatment. Mean energy settings were 14.9±2.0 J/cm2 for HR and 17.1±0.6 J/cm2 for HR-D. Longer pulse widths were applied in case of HR-D treatment. Hair counts and photographic evaluation of skin sites were made at baseline and at the last follow-up. Final overall evaluations were performed by patients and clinicians. RESULTS Average clearances of 52.8% and 83.4% were achieved by HR and HR-D, respectively. No significant adverse effects were reported after HR-D treatment. One case each of hypopigmentation and hyperpigmentation was reported for HR. CONCLUSION An IPL source by removing 45 nm of the emitted spectra and applying longer pulse width was found to provide a safer and more effective means of photoepilation in Asian patients. [source] Variable-Pulse Nd:YAG Laser in the Treatment of Facial TelangiectasiasDERMATOLOGIC SURGERY, Issue 1 2006AVERY A. BEVIN MD BACKGROUND Variable-pulse 1,064 nm wavelength lasers have been used with good effectiveness on leg telangiectasias and reticular veins and have shown promising results on facial telangiectasias as well. OBJECTIVE To investigate the effectiveness of a variable-pulse neodymium:yttrium-aluminum-garnet (Nd:YAG) laser using a small spot size in the treatment of facial telangi-ectasias. METHODS Eight male patients (mean age 75 years) underwent a single treatment session using a variable-pulse 1.5 mm spot size Nd:YAG laser with epidermal cooling. Telangiectasia diameters were 0.3 to 2.0 mm. Test sites were performed using three pulse widths (3, 20, and 60 ms), with fluences varying depending on vessel size and response. Full treatments were per-formed using test parameters giving the best response. Thirteen weeks later, the patients returned for final evaluation and satisfaction rating. RESULTS Fluences ranged from 226 to 425 J/cm2, with smaller vessels requiring larger energies. Pulse duration was equally divided between the 20 and 60 ms settings. The shortest pulse width (3 ms) was inferior in all patients. Longer pulse durations achieved superior vessel elimination with minimal immediate purpura and no postinammatory hyperpigmentation. The average mean vessel clearance was 26 to 50% in half of the patients and 51 to 75% in the other half as evaluated by three unbiased dermatologists with extensive laser experience. CONCLUSION A small,spot size Nd:YAG laser using a pulse width of 20 ms or higher appears to be effective in clearing a significant percentage of facial telangectasias with a single pass. The side effects were minimal. [source] Laser Hair Removal: Long-Term Results with a 755 nm Alexandrite LaserDERMATOLOGIC SURGERY, Issue 11 2001Sorin Eremia MD Background. Hypertrichosis is a common problem for which laser hair removal is becoming the treatment of choice. Optimal wavelength, pulse duration, spot size, fluence, and skin cooling parameters for various skin types have not yet been firmly established. Objective. To evaluate the long-term efficacy and safety of a 3-msec 755 nm alexandrite laser equipped with a cryogen cooling device for patients with Fitzpatrick skin types I,V. Methods. Eighty-nine untanned patients with skin types I,V underwent a total of 492 treatments of laser hair removal over a 15-month period. Each patient in the study underwent a minimum of three treatment sessions spaced 4,6 weeks apart (mean treatments 5.6). Retrospective chart review and patient interviews were used to establish hair reduction results. Treatment sites included the axillae, bikini, extremities, face, and trunk. A 3-msec pulse width, 755 nm alexandrite laser equipped with a cryogen spray cooling device was used in this study. Spot sizes of 10,15 mm were used. A spot size of 10 mm was used for fluences greater than 40 J/cm2, a spot size of 12 mm was used for fluences of 35,40 J/cm2, and spot sizes of 12 and 15 mm were used for fluences less than 30 J/cm2. Fluences ranging from 20 to 50 J/cm2 (mean fluence 36 J/cm2) were used. Results. The patients had a mean 74% hair reduction. Skin type I patients had an average of 78.5% hair reduction using a mean fluence of 40 J/cm2 (35,50 J/cm2) and a 10,12 mm spot size (12 mm in more than 95% of treatments). Skin type II patients had a mean 74.3% hair reduction using a mean fluence of 38 J/cm2 (30,40 J/cm2) and a 12,15 mm spot size. Skin type III patients had a mean 73.4% hair reduction using a mean fluence of 37 J/cm2 (25,40 J/cm2) and a 12,15 mm spot size. Skin type IV patients had a mean 71.0% hair reduction using a mean fluence of 31 J/cm2 (25,35 J/cm2) and a 12,15 mm spot size. A patient with skin type V had a 60% hair reduction using a mean fluence of 23 J/cm2 (20,25 J/cm2) and a 12,15 mm spot size. The efficiency of hair removal directly correlates significantly with the fluence used. Rare side effects included transient postinflammatory hyperpigmentation (n = 9; 10%), burn with blisters (n = 1; 1%), and postinflammatory hypopigmentation (n = 2; 2%). All complications resolved without permanent scarring. Conclusion. The 3-msec cryogen cooling-equipped alexandrite laser can safely and effectively achieve long-term hair removal in patients with skin types I,V. The best results are achieved in untanned patients with skin types I,IV. [source] Laser Hair Removal with Alexandrite versus Diode Laser Using Four Treatment Sessions: 1-Year ResultsDERMATOLOGIC SURGERY, Issue 11 2001Sorin Eremia MD Background. Laser hair removal is the treatment of choice for hypertrichosis. The two most commonly used hair removal lasers are compared. Objective. To present the results of a comparative study examining the role of wavelength, fluence, spot size, pulse width, and cooling systems on long-term results after a series of four laser hair removal treatments using the 755 nm alexandrite and 800,810 nm diode lasers. Methods. The axillae of 15 untanned, type I,V patients were treated side by side four times at 4- to 6-week intervals with a 755 nm, 3-msec pulse width, cryogen spray-equipped alexandrite laser and an 800 nm, variable pulse width, cooled sapphire window-equipped diode laser. Each patient was pretested and treated with the maximum fluence tolerated at the largest spot size available for each laser (12 mm round/113 mm2 for the alexandrite and 9 mm for the diode). Results. Evaluations were done at 3, 6, 9, and 12 months after the last treatment. Twelve-month results with the alexandrite and diode lasers achieved 85% versus 84% hair reduction. The fact that tan avoidance was strictly followed permitted the use of relatively high fluences (25,30+ J/cm2) even in type IV patients. For most patients, four treatment sessions using high fluences (30,40 J/cm2) with relatively large spot sizes (12 mm round for the 755 nm alexandrite and 9 mm for the 800 nm diode) resulted in 12-month hair reductions in the 90% range. Conclusion. Both the alexandrite and diode lasers in this 12-month study produced excellent long-term hair reductions. [source] The Effects of Variable Pulse Width of Er:YAG Laser on Facial SkinDERMATOLOGIC SURGERY, Issue 4 2001Khalil A. Khatri MD Background. The use of CO2 and Er:YAG lasers for resurfacing has increased significantly in the past few years. Er:YAG laser causes pinpoint bleeding during and after treatment with a typical pulse width of 250 ,sec. A longer pulse of Er:YAG laser can potentially coagulate dermal blood vessels and increase the residual thermal damage (RTD). Objective. To evaluate the effects of various pulse durations of Er:YAG laser on the depth of RTD and bleeding. Methods. The preauricular skin of a volunteer was exposed to Er:YAG laser at 250-, 350-, and 700-,sec pulse durations, with a fluence of 5 J/cm2. The number of passes varied between 6 and 16. The treated skin was excised and a histologic evaluation was done. Results. The maximum depth of RTD was 50 ,m and there was decreased bleeding with a 700-,sec pulse duration. Conclusion. The increased pulse duration of Er:YAG laser of 700 ,s does not increase the maximum reported RTD and therefore would not change the recovery time and may have a beneficial effect on hemostasis. [source] Spin Echo Analysis of Restricted Diffusion under Generalized Gradient Waveforms for Spherical Pores with Relaxivity and InterconnectionsISRAEL JOURNAL OF CHEMISTRY, Issue 1-2 2003Brett N. Ryland The problem of restricted diffusion in spherical pores is examined under conditions of finite gradient pulse width in pulsed gradient spin echo (PGSE)-NMR experiments. Closed form analytic expressions are derived, and the case of interconnected pores is briefly examined. An expression, based on the pore hopping approximation, is presented that predicts the echo attenuation for diffusion between pores under any gradient waveform. [source] Enhanced healing of diabetic foot ulcers using local heat and electrical stimulation for 30 min three times per weekJOURNAL OF DIABETES, Issue 1 2010Jerrold Scott PETROFSKY Abstract Background:, Electrical stimulation (ES) with heating is effective in healing chronic wounds. However, it this effect due to ES alone or both heating and ES? The aim of the present study was to deduce the individual roles of heat and ES in the healing of chronic wounds. Methods:, The study was performed on 20 patients (mean age 48.4 ± 14.6 years) with non-healing diabetic foot ulcers (mean duration 38.9 ± 23.7 months) who received local dry heat (37°C; n = 10) or local dry heat + ES (n = 10) three times a week for 4 weeks. Patients were given ES using biphasic sine wave stimulation (30 Hz, pulse width 250 ,s, current approximately 20 mA). Results:, Skin blood flow in and around the wound was measured with a laser Doppler flow imager. In the ES + heat group, the average wound area and volume decreased significantly by 68.4 ± 28.6% and 69.3 ± 27.1%, respectively (both P < 0.05), over the 1-month period. During the average session, blood flow increased to 102.3 ± 25.3% with local heat and to 152.3 ± 23.4% with ES + heat. In the group receiving treatment with local heat only, wounds that had not healed for at least 2 months showed 30.1 ± 22.6% healing (i.e. a decrease in wound area) after 1 month. Although this level of healing was significant, it was less than that observed in the ES + heat group (P < 0.05). Conclusions:, Local dry heat and ES work well together to heal chronic diabetic foot wounds; however, local heat would appear to be a relevant part of this therapy because ES alone has produced little healing in previous studies. [source] Molecular dynamics simulations of MALDI: laser fluence and pulse width dependence of plume characteristics and consequences for matrix and analyte ionizationJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2010Richard Knochenmuss Abstract Molecular dynamics simulations of matrix-assisted laser desorption/ionization were carried out to investigate laser pulse width and fluence effects on primary and secondary ionization process. At the same fluence, short (35 or 350 ps) pulses lead to much higher initial pressures and ion concentrations than longer ones (3 ns), but these differences do not persist because the system relaxes toward local thermal equilibrium on a nanosecond timescale. Higher fluences accentuate the initial disparities, but downstream differences are not substantial. Axial velocities of ions and neutrals are found to span a wide range, and be fluence dependent. Total ion yield is only weakly dependent on pulse width, and consistent with experimental estimates. Secondary reactions of matrix cations with analyte neutrals are efficient even though analyte ions are ablated in clusters of matrix. Copyright © 2010 John Wiley & Sons, Ltd. [source] Inactivation of orange juice peroxidase by high-intensity pulsed electric fields as influenced by process parametersJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2006Pedro Elez-Martínez Abstract The inactivation of orange juice peroxidase (POD) under high-intensity pulsed electric fields (HIPEF) was studied. The effects of HIPEF parameters (electric field strength, treatment time, pulse polarity, frequency and pulse width) were evaluated and compared with conventional heat pasteurization. Samples were exposed to electric field strengths from 5 to 35 kV cm,1 for up to 1500 µs using square wave pulses in mono- and bipolar mode. Effect of pulse frequency (50,450 Hz), pulse width (1,10 µs) and electric energy on POD inactivation by HIPEF were also studied. Temperature was always below 40 °C. POD was totally inactivated by HIPEF and the treatment was more effective than thermal processing in inactivating orange juice POD. The extent of POD inactivation depended on HIPEF processing parameters. Orange juice POD inhibition was greater when the electric field strength, the treatment time, the pulse frequency and the pulse width increased. Monopolar pulses were more effective than bipolar pulses. Orange juice POD activity decreased with electric energy density input. The Weibull distribution function adequately described orange juice POD inactivation as a function of the majority of HIPEF parameters. Moreover, reduction of POD activity related to the electric field strength could be well described by the Fermi model. Copyright © 2005 Society of Chemical Industry [source] Continuous wave and passively Q-switched laser performance of the mixed crystal Nd:Lu0.15Y0.85VO4LASER PHYSICS LETTERS, Issue 5 2010S. Zhang Abstract Laser characteristics of a novel mixed laser crystal Nd:Lu0.15Y0.85VO4 was investigated. It is attractive for Q-switching with high repetition rate and short pulse width due to its suitable stimulated emission cross-section and short upper level lifetime. Continuous wave (CW) output power of 8.18 W was obtained at the pump power of 18.9 W, corresponding to the optical conversion efficiency of 43.3% and the slope efficiency of 47%. In the passive Q-switching operation, the minimum pulse width attained was 7.8 ns, with the pulse repetition frequency of 23.2 kHz, with the single pulse energy and peak power estimated to be 94.8 ,J and 12.2 kW, respectively. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Laser properties of continuous-grown GdVO4/Nd:GdVO4 composite crystalLASER PHYSICS LETTERS, Issue 9 2009X.D. Li Abstract Effective CW and A-O Q-switched laser operations were demonstrated firstly using a continuous-grown GdVO4/Nd:GdVO4 composite rod. A maximum CW output power of 19.2Wwas obtained with the slope efficiency of 79.6% and the maximum optical-optical efficiency of 73.0% to absorbed pump power. In A-O Q-switched operation, the pulse width of 15.0 ns, 10.6 ns, and 6.9 ns, the peak power of about 11.3 kW, 29.6 kW, and 130.4 kW were achieved at the repetition rate of 100 kHz, 50 kHz, and 10 kHz, respectively. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laserLASER PHYSICS LETTERS, Issue 8 2007H. Lei Abstract A stable repetition rate continuously controllable passively Q-switched Nd:YAG bonded microchip laser is presented. A 0.8 mm-thickness 7 mm-diameter Nd:YAG crystal at 1.6 at.% is adapted as active medium and the saturable absorber for passively Q-switched pulse generating, a 0.2 mm-thickness 6.8-mm diameter Cr4+:YAG piece was thermal bonded into the Nd:YAG after primary optical contact. By using pulse pump and controlling the duty cycle of electric pulse and temperature of laser diode, a 1 W C-mount packaged fast-collimated laser diode, we can continuously achieve repetition rate from 1 kHz to 10 kHz as active Q-switched laser. The delay time at 10 kHz is 90 ,s, while the single pulse energy is 2.8 ,J with pulse width of 2 ns. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] A c-cut Nd:GdVO4 solid-state laser passively Q-switched with Co2+:LaMgAl11O19 lasing at 1.34 µmLASER PHYSICS LETTERS, Issue 8 2007H.-J. Qi Abstract We investigated a high power diode-laser pumped passively Q-switched c-cut Nd:GdVO4 solid-state laser, lasing at 1.34 µm, with a Co2+:LaMgAl11O19 saturable absorber. With the optimum output coupler transmission T = 5.5% and pump power of 11.5 W, the static output power of 3.01 W was obtained. The passively Q-switching operation with Co:LMA (initial transmission T0 = 90%) as saturable absorber, shows that the shortest output pulse width, the highest output power, the highest pulse repetition and the highest pulse peak power were 32 ns, 266 mW, 277 kHz, and 187 W, respectively. (© 2007 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Switchable pulses generation in passively Q-switched multilongitudinal-mode microchip laserLASER PHYSICS LETTERS, Issue 2 2007J. Dong Abstract Periodical switching laser pulses with nanosecond pulse width and several kilowatts peak power from wideseparated multilongitudinal-mode oscillation were observed experimentally in laser-diode pumped passively Q-switched Yb:YAG microchip laser with Cr4+:YAG as saturable absorber. Pulses from different longitudinal modes oscillate alternatively. Periodical pulses oscillation dynamics induced by spatial hole burning effect and mode competition was investigated numerically by the evolution of the inversion population of different modes and the bleaching and recovery of the inversion population of the saturable absorber. The numerical simulations of switchable periodical pulsation of multilongitudinal-mode passively Q-switched Yb:YAG/Cr4+:YAG microchip lasers are in good agreement with experimental results and confirmed that such pulsations are an intrinsic property in passively Q-switched Yb:YAG/Cr4+:YAG microchip lasers. (© 2007 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Electro-optic Q-switched Yb:YAG slab laserLASER PHYSICS LETTERS, Issue 5 2006Q. Liu Abstract A novel side-pumped structure with microlens-free diode arrays and a lensduct was demonstrated. This structure is much more robust and simple than traditional approach of a microlens-conditioned diode arrays with a lensduct. A quasi-CW diode arrays side-pumped KD*P Q-switched Yb:YAG slab laser has been demonstrated. An output energy of ,10 mJ/pulse with pulse width as short as ,20ns is obtained at 1,10 Hz repetition rate. To our knowledge, this is the shortest pulse width of Electro-optic Q-switched laser output by using Yb:YAG as the gain medium. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Soliton propagation in an absorbing three-level atomic systemLASER PHYSICS LETTERS, Issue 8 2004H. Eleuch Abstract We present analytic results of soliton shapes propagating in an absorbing three-level atomic system in the lambda configuration which is excited by a CWfield at the Stokes transition. We find analytic relations for the control of the propagation velocity which can be influenced by the pulse width and by the intensity and polarization of the CW field. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Cavity preparation using a superpulsed 9.6-,m CO2 laser,a histological investigationLASERS IN SURGERY AND MEDICINE, Issue 5 2002R. Müllejans Abstract Background and Objectives The superpulsed 9.6-,m CO2 laser is an effective laser for ablating dental tissues and decay. This histological study compares laser class V preparations with conventional treatment to evaluate the resulting formation at the cavity walls. Study Design/Materials and Methods Four class V preparations (one made with a diamond drill and three with the CO2 laser (9.6 ,m, 60 microseconds pulse width, 40 mJ pulse energy, 100 Hz, integrated scanner system, water cooling) were performed on ten extracted teeth. The cavities were filled with a composite resin partly including enamel and dentine conditioning. Results After laser preparation, no cracks or signs of carbonisation were detected. The results were comparable to those attained with conventional treatment. Following cavity filling without prior conditioning, gaps were noted at the cavosurface indicating a lack of adhesion. Dentinal bonding decreased gap formation significantly. Conclusion The 9.6-,m CO2 laser is an effective tool for cavity preparation. Lasers Surg. Med. 30:331,336, 2002. © 2002 Wiley-Liss, Inc. [source] A CMOS differential fifth-derivative Gaussian pulse generator for UWB applicationsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 8 2010Jin He Abstract A CMOS differential fifth-derivative Gaussian pulse generator is presented for Ultrawideband (UWB) applications. The design exhibits low-power consumption, low-circuit complexity, and precise pulse shape to inherently comply with the FCC spectrum mask for indoor UWB applications without the need for a filter. The proposed differential pulse generator was implemented with a 1.8-V, 0.18-,m CMOS process, but only the positive fifth-derivative Gaussian pulse was measured owing to the limitation of the available testing facilities. The measured pulse has peak-to-peak amplitude of 154 mV and a pulse width of 820 ps. Small core area of the differential pulse generator is only 0.028 mm2 because of its all digital circuit design. The average power dissipation is 1.2 mW with a pulse repetition frequency (PRF) of 50 MHz. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1849,1852, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25342 [source] Experimental investigation into femtosecond fiber ring laser with passive mode lockingMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Xiaoping Xie Abstract A passively mode-locked Er3+ -doped fiber ring laser is experimentally investigated, with the emphasis on its practical design by considering the effects of ring cavity length, pumping light power, and optical amplification on the femtosecond optical pulses obtained. It is shown that the designed fiber ring laser can operate at the center wavelength of 1550 nm to produce a train of periodic optical pulses with full width at half maximum (FWHM) of 270 fs, repetition frequency of 20 MHz, and average output optical power of 146 ,W. The resulting femtosecond optical pulses are then amplified by using three kinds of Er3+ -doped optical fibers with different lengths and Er3+ -doped concentrations, respectively, while employing the same pumping laser. In the experiments, both the FWHM of amplified optical pulses and the amplifier gain are measured under different conditions. The optimization of optical pulse width is also carried out in terms of pumping light power. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 63,67, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23985 [source] The power/frequency-dependent pulse width and jitter of a 1.55 ,m Fabry,Perot laser diode transmitterMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2001Gong-Ru Lin Abstract The effect of detuning the frequency and power of an electrical comb generator on the peak power, pulse width, and timing jitter of a 1.55 ,m Fabry,Perot laser diode transmitter operating in the gain-switching mode is discussed. The optimal frequencies for achieving the lowest timing jitter (510 MHz), the shortest pulse width (535 MHz), and the largest power (460 MHz) that deviated from theoretical predictions are obtained. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 232,234, 2001. [source] 12 Effects of synchronized intestinal electrical stimulation on small intestinal motility in dogsNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2006J YIN Our previous studies showed that synchronized gastric electrical stimulation enhanced antral contractions, accelerated gastric emptying in dogs. It has never been reported whether synchronized electrical stimulation could improve small intestinal motility. The aim of this study was to investigate the effects of synchronized intestinal electrical stimulation (SIES) on small bowel motility in both fasting and fed states in dogs. Methods:, Five healthy female dogs (18,24 kg) were equipped with a duodenal cannula for the measurement of small bowel motility using manometry. Two pairs of bipolar electrodes were implanted on the small intestinal serosa with an interval of 25 cm; the first one was 10 cm beyond the pylorus and used for stimulation. The experiment was consisted of four sessions in each dog with a randomized order. In the fasting state, 20 min after occurrence of phase III, SIES was initiated and maintained for 45 min, small bowel motility was recorded during the entire experiment, and no stimulation was performed in the control session. In other two sessions, dogs were fed with solid meal at the beginning of the experiment; glucagon (0.1 mg kg1) was injected 20 min after feeding, SIES was initiated at the same time for 20 min followed by 20 min recovery period. The stimulus was composed of train of pulses with on-time of 0.5 s, frequency of 20 Hz, pulse width of 2 ms and amplitude of 4 mA. Results:, 1). In the fasting state, SIES induced small intestinal contractions during phase I. The motility index was 5.2 ± 0.6 in the control session and significantly increased to 10.3 ± 0.7 with SIES (P = 0.003). 2). In the fed state, glucagon substantially and significantly inhibited small intestinal motility. The motility index was 11.3 ± 0.7 after feeding and reduced to 3.4 ± 0.5 with glucagon injection (P < 0.001). SIES significantly enhanced glucagon-induced small intestinal postprandial hypomotility. The motility index was 3.4 ± 0.5 in the control session and increased to 6.0 ± 0.3 with the presence of SIES (P = 0.03). Conclusions:, Intestinal electrical stimulation synchronized with intestinal slow waves induces intestinal contractions during phase I and enhanced small intestinal postprandial hypomotility induced by glucagon. SIES may have the therapeutic potential for treating small intestinal motility disorders. (Supported by a grant from American Diabetes Association). [source] 46 The feasibility of duodenum electrical stimulation to produce gastrointestinal symptoms in a clinical trialNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2006KA STECCO Introduction:, Proximal duodenal electrical stimulation with various energy parameters has been investigated as a possible treatment for various gastrointestinal (GI) myoelectrical diseases. Wide pulse width (millisecond) stimulation in the proximal duodenum can disrupt or entrain the normal myoelectrical rhythm and provide a potential feedback pathway to alter normal gastric function such as emptying, fundus tone, and intra-gastric pressure and subsequently produce specific symptoms that could affect eating behaviors. A specific level of electrical stimulation is necessary to elicit symptoms and serve as an indicator that energy parameters are adequate. However, there has been no published data correlating electrical threshold stimulation with symptom characterization. The goal of this study was to determine the average minimum pulse width necessary to elicit GI symptoms. Methods:, Eight patients underwent endoscopic placement of intraluminal electrodes in the proximal duodenum. Each patient received electrical stimulation in the millisecond (ms) range starting with a pulse width of 100 ms that was increased by intervals of 100 ms up to a maximum pulse width of 500 ms. The pulse repetition frequency was fixed at 12 CPM and each regimen was repeated for amplitudes ranging from 2 milliamps (mA) to 10 mA. Gastrointestinal symptom scores consisting of nausea, vomiting, satiety, fullness, pain, bloating and other, were taken at baseline and after each regimen change. Results:, There was an average minimum threshold necessary for elicitation of symptoms (293.7 + 41.7 ms, p-value = 0.063). The three most frequently reported GI symptoms were crampy abdominal pain, fullness, and bloating. Conclusions:, Electrical stimulation of the duodenum is feasible. A certain minimum threshold of duodenal electrical stimulation is necessary to elicit GI symptoms in patients. The intensity and patient tolerability of each specific GI symptom was able to be adjusted by changing a certain energy parameter within a regimen. Further research is warranted to evaluate the ability of duodenal electrical stimulation to produce GI symptoms that may alter eating behaviors. [source] 47 Effects of retrograde gastric electrical stimulation on gastric motility and plasma hormones in dogsNEUROGASTROENTEROLOGY & MOTILITY, Issue 6 2006G SONG Aims:, The aim of this study was to investigate the effect of different parameters of RGES with trains of long pulses in turning gastric slow waves into tachygastria, and evaluate the effects of RGES with the efficient trains of pulses on gastric slow waves, gastric emptying of solids and plasma concentrations of satiety-related peptides and glucose. Methods:, Seven female dogs implanted with four pairs of gastric electrodes were studied in two experiments. The first experiment included a series of sessions with different pacing parameters in the fasting state, each lasting 10 min. The second experiment included two randomized sessions (control and RGES). Gastric emptying of solid was measured by scintigraphy for a period of 4 h. Blood samples were collected at 45 and 15 min before, 30, 60 and 120 min after the meal. Plasma leptin, insulin and glucagon were measured using radioimmunoassay method. Plasma glucose was assessed with a commercially available glucometer. RGES was applied via the distal pair of electrodes (2 cm above the pylorus) with trains of pulses. RGES was initiated 30 min before the first blood sample and maintained for a period of 2.5 h. Gastric slow waves and symptomatic response were also recorded in each session. Results:, (1) RGES with pulse trains (12 trains/min) was able to turn regular gastric slow waves into tachygastria. (2) RGES with the efficient parameters (frequency: 40 Hz; pulse width: 2 ms; amplitude: 5 mA; train on-time, 2 s; off-time, 3 s) was capable of delaying gastric emptying of solids (P < 0.05). (3) Compared with the control session without RGES, the total AUC's of plasma insulin with RGES was significantly decreased in the fasting and postprandial periods (p < 0.05). However, the total area under curves (AUC's) of plasma leptin, glucagon, and glucose were not significantly affected by RGES (p > 0.05). (4) This method of GES induced no noticeable symptoms. Conclusion:, RGES with at a tachygastrial frequency decreases gastric emptying of solids and plasma insulin, but has no effects on plasma leptin, glucagons, and glucose. [source] Efficacy and efficiency of gastric electrical stimulation with short pulses in the treatment of vasopressin-induced emetic responses in dogsNEUROGASTROENTEROLOGY & MOTILITY, Issue 5 2006G. Song Abstract, The aim of this study was to determine the most effective and efficient anti-emetic parameters of short-pulse gastric electrical stimulation (GES) in dogs. Seven female beagle dogs implanted with four pairs of gastric electrodes were studied in eight randomized sessions (saline, vasopressin, and six GES sessions with different parameters). Each session consisted of four 20-min recordings of gastric slow waves and symptoms. In sessions 1 and 2, saline and vasopressin, respectively, were infused during the second 20-min period. The protocol of the other six sessions was the same as session 2 except that GES was continuously applied. It was found that: (1) vasopressin induced gastric dysrhythmia and emetic response (P < 0.01, anova); (2) short-pulse GES with a frequency of 14 or 40 Hz and pulse width of 0.1 or 0.3 ms, but not 0.6 ms was able to reduce symptoms induced by vasopressin; (3) short-pulse GES with a pulse width of 0.3 ms was the most effective in preventing vasopressin-induced symptoms; (4) none of the tested GES methods improved vasopressin-induced gastric dysrhythmia. We conclude that vasopressin induces gastric dysrhythmia and symptoms. Short-pulse GES with a pulse width of 0.3 ms and frequency of 14 Hz is most effective and efficient in preventing vasopressin-induced emetic responses in dogs. [source] Electric Parameters Optimization in Spinal Cord Stimulation.NEUROMODULATION, Issue 4 2010Study in Conventional Nonrechargeable Systems Background:, Spinal cord stimulation devices provide a means of creating an electric field. The parameters used to produce this electric field are: pulse amplitude, pulse width (Pw), and pulse frequency (F). Aims:, The purpose is to document the effects that the various stimulus parameters have on patient perception of paresthesia and the relationship that this perception has on pain relief. Methods:, Stimulus parameters were varied independently keeping the electrode polarity constant while recording stimulation thresholds. The Pw was varied from 195 to 300 µsec while maintaining the frequency at 50 Hz. The F was varied from 10 to 100 Hz while maintaining the Pw at 300 µsec. We also measured the paresthesia coverage percentage and the subjective perception of quality reported by the patients with each one of the parameter changes. Results:, There was a statistically significant correlation between Pw and all the stimulation thresholds. As for the therapeutic range, the differences observed also were statistically significant. Pw variation did not produce significant differences in coverage and subjective quality of the paresthesia. The perception threshold did not vary significantly with F changes. However, F significantly affected both coverage of the painful area and paresthesia perception quality. Conclusions:, In the usual Pw ranges, it seems that its usefulness is limited to obtaining finer adjustments in the stimulation amplitude. Frequency management may be significantly useful to get a wider coverage of the stimulated area. [source] Stimulation of the rat somatosensory cortex at different frequencies and pulse widthsNMR IN BIOMEDICINE, Issue 1 2006N. Van Camp Abstract Functional MRI (fMRI) during electrical somatosensory stimulation of the rat forepaw is a widely used model to investigate the functional organization of the somatosensory cortex or to study the underlying mechanisms of the blood oxygen level-dependent (BOLD) response. In reality, somatosensory stimuli have complex timing relationships and are of long duration. However, by default electrical sensory stimulation seems to be performed at an extremely short pulse width (0.3,ms). As the pulse duration may alter the neuronal response, our aim was to investigate the influence of a much longer stimulus pulse width (10,ms) using BOLD fMRI during electrical forepaw stimulation. The optimal neuronal response was investigated by varying the stimulus frequency at a fixed pulse duration (10,ms) and amplitude (1,mA). In a parallel experiment we measured the neuronal response directly by recording the somatosensory evoked potentials (SEPs). Quantification of the BOLD data revealed a shift in the optimal response frequencies to 8,10,Hz compared with 1,Hz at 0.3,ms. The amplitude of the recorded SEPs decreased with increasing stimulation frequency and did not display any correlation with the BOLD data. Nevertheless, the summated SEPs, which are a measure of the integrated neuronal activity as a function of time, displayed a similar response profile, with a similar maximum as observed by relative BOLD changes. This shift in optimal excitation frequencies might be related to the fact that an increased pulse width of an electrical stimulus alters the nature of the stimulation, generating also sensorimotor instead of merely somatosensory input. This may influence or alter the activated pathways, resulting in a shift in the optimal response profile. Copyright © 2006 John Wiley & Sons, Ltd. [source] Use of an Intracardiac Electrogram Eliminates the Need for a Surface ECG during Implantable Cardioverter-Defibrillator Follow-UpPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2007KEVIN A. MICHAEL M.B.Ch.B. Background:A surface electrocardiogram (SECG) for pacing threshold measurements during routine implantable cardioverter-defibrillator (ICD) follow-up can be cumbersome. This study evaluated the use of an intrathoracic far-field electrogram (EGM) derived between the Can and superior vena cava (SVC) electrode,the Leadless electrocardiogram (LLECG), in dual chamber ICDs in performing pacing threshold tests. Methods:The LLECG was evaluated prospectively during atrial and ventricular pacing threshold testing as a substudy of the Comparison of Empiric to Physician-Tailored Programming of Implantable Cardioverter-Defibrillators trial (EMPIRIC) in which dual chamber ICDs were implanted in 888 patients. Threshold tests were conducted at 1 volt by decrementing the pulse width. Follow-up at three months compared pacing thresholds measured using LLECG with those using Lead I of the surface ECG (SECG). The timesaving afforded by LLECG was assessed by a questionnaire. Results:The median threshold difference between LLECG and SECG measurements for both atrial (0.00 ms, P = 0.90) and ventricular (0.00 ms, P = 0.34) threshold tests were not significant. Ninety percent of atrial and ventricular threshold differences were bounded by ± 0.10 ms and ,0.10 to +0.04 ms, respectively. We found that 99% of atrial and ventricular thresholds tests at six and 12 months attempted using LLECG were successfully completed. The questionnaire indicated that 65% of healthcare professionals found LLECG to afford at least some timesaving during device follow-ups. Conclusion:Routine follow-up can be performed reliably and expeditiously in dual chamber Medtronic (Minneapolis, MN, USA) ICDs using LLECG alone, resulting in overall timesaving. [source] Polarization-resolved degenerate four-wave mixing of CdS nanocrystals in a nonresonant regionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2006S. M. Ma Abstract The third-order susceptibilities of various concentrations of TOPO-passivated CdS nanocrystals (NCs) with the size near the Bohr radius were investigated using polarization-resolved degenerate four-wave mixing (DFWM) in a nonresonant excitation region with 532 nm wavelength and 8 ns pulse width. The second hyperpolarizabilities ,,hxxxx, and ,,hxyyx, of the CdS NCs were ,1.25 × 10,42 m5/V2 and ,3.66 × 10,43 m5/V2, respectively. The ratio (,,hxyyx,/,,hxxxx,) of the hyperpolarizabilities was ,0.29 that indicated a large contribution of electronic polarization process to the third-order nonlinearity of CdS NCs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||