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At least 145 records · Page 8Linked to original sources
PubMed1979

Laser flow cytometric light scatter and fluorescence pulse width and pulse rise-time sizing of mammalian cells.

In laser flow cytometry, an increasingly popular technique of analytical cytology, quantitative measurements of interest include cell and nuclear diameters. Electronic circuitry for a new cell sizing technique has been developed which measured the time that signal pulses from either fluorescence or light scatter sensors exceed a preset constant fraction of the peak signal amplitude (pulse width) or the time that it takes a signal to rise between constant fractions of the peak signal amplitude on the rising side of the pulse (pulse rise-time). These pulse width or pulse rise-time measurements were related to cell or nuclear diameters and were used in combination to determine nuclear size to cell size ratios. This method of sizing was found to be independent of fluorescent or light-absorbing stain intensity, linearly related to cell or nuclear diameter, and capable of resolving small diameter differences.

Animals↗
PubMed2006

Amplified reference pulse storage for low-coherence pulsed Doppler lidar.

We present a lidar concept for wind-speed measurements, in which a pulsed laser is used as the source for measurement and reference beams. A fraction of the transmitted pulse is stored in a fiber-optic ring resonator with a path length longer than the pulse. The output of the resonator is a pulse train that is used as the reference beam and can be mixed with the Doppler-shifted measurement signal. Because this reference has traveled a distance equivalent to the measurement beam's path length, low-coherence sources can be used. Inserting an erbium-doped fiber amplifier into the resonator ensures that the stored pulses do not decay in amplitude. Experiments prove that 16 reference pulses of sufficiently constant amplitude and stability can be generated. This would correspond to a measurement range of 240 m in free air over which the returned signal is sampled at equal intervals. Velocity measurements of a hard target have been carried out in the range of 1-10 m/s. The Doppler-measured velocities agree with tachometer reference measurements within +/-0.09 m/s.

Journal Article↗
PubMed2006

Dual-stage soliton compression of a self-started additive pulse mode-locked erbium-doped fiber laser for 48 fs pulse generation.

A dual-stage single-mode fiber (SMF) and large-effective-area fiber (LEAF) link for generating 48 fs pedestal-free pulses from a 40 MHz self-started additive pulse mode-locked erbium-doped fiber laser (APM-EDFL) with output peak power and pulse energy of 16 kW and 500 pJ, respectively, is demonstrated. With the SMF+LEAF link, a maximum pulse-width compression ratio of 7 and an optimized pulse-energy confining ratio of up to 85% can be achieved, and the soliton self-frequency shift effect of the APM-EDFL pulse can be greatly suppressed.

Journal Article↗
PubMed1996

Pulsed light and pulsed electric field for foods and eggs.

Two new technologies for use in the food industry are described. The first method discussed uses intense pulse of light. This pulsed light (PureBright) process uses short duration flashes of broad spectrum "white" light to kill all exposed microorganisms, including vegetative bacteria, microbial and fungal spores, viruses, and protozoan oocysts. Each pulse, or flash, of light lasts only a few hundred millionths of a second (i.e., a few hundred microseconds). The intensity of each flash of light is about 20,000 times the intensity of sunlight at the earth's surface. The flashes are typically applied at a rate of about one to tens of flashes per second. For most applications, a few flashes applied in a fraction of a second provide an effective treatment. High microbial kill can be achieved, for example, on the surfaces of packaging materials, on packaging and processing equipment, foods, and medical devices as well as on many other surfaces. In addition, some bulk materials such as water and air that allow penetration of the light can be sterilized. The results of tests to measure the effects of pulsed light on Salmonella enteritiditis on eggs are presented. The second method discussed uses multiple, short duration, high intensity electric field pulses to kill vegetative microorganisms in pumpable products. This pulsed electric field (or CoolPure) process can be applied at modest temperatures at which no appreciable thermal damage occurs and the original taste, color, texture, and functionality of products can be retained.

Animals↗
PubMed2003

Treatment of telangiectasia using the multi-pass technique with the extended pulse width, pulsed dye laser (Cynosure V-Star).

BACKGROUND: The pulsed dye laser (PDL) has been used for the treatment of facial and leg telangiectasia, where it provides safe and effective treatment. Often, a single treatment with the PDL can provide acceptable vessel clearance. Unfortunately, the hallmark of PDL treatment is transient purpura, which can be cosmetically unacceptable to patients. A new class of PDL has been developed in an effort to reduce this transient side effect while maintaining both safety and efficacy. OBJECTIVE: To evaluate the ability of multi-pass treatment for telangiectasia with extended pulse width (40 ms) PDL to provide effective, single-treatment vessel treatment without inducing purpura. METHODS: A total of 40 patients presenting with facial or leg telangiectasia were treated with the extended pulse width PDL (595 nm), used in conjunction with refrigerated air-cooling (SmartCool; Cynosure). Treatment was given using a pulse width of 40 ms and fluences at or below the purpuric threshold (less than 16 J/cm(2)) and with high-flow air cooling at -4 degrees C. Up to three passes were given until vessel disappearance or intravascular coagulation was observed. A second treatment was done, where needed, 4-8 weeks following the initial treatment. Patients were evaluated 4, 8, and 12 weeks after the final treatment. RESULTS: Following a single treatment, 70% of facial and 80% of leg vessels exhibited at least 75% clearance. After two treatments, 14/20 leg vessels cleared at 75-100%. In all cases, vessel clearance was associated with transient purpura lasting less than 7 days. Hyperpigmentation occurred in 5% of facial vessels and 55% of leg veins. Sub-purpuric doses did not provide acceptable single-treatment clearance. CONCLUSIONS: Extended pulse width dye lasers significantly increase the threshold for purpura, allowing higher fluences to be employed. For the goal of single treatment vessel clearance, the extended pulse duration provided acceptable, single-treatment improvement but only in the presence of purpura. While additional, non-purpuric treatments may provide acceptable outcomes, additional improvements will be necessary to provide consistent, effective, single-treatment clearance of telangiectasia without generalized purpura.

Face↗
PubMed2004

Velocity pulse advances pressure pulse by close to 45 degrees in the rat pial arterioles.

In order to clarify the phase relationship between velocity pulse and pressure pulse propagating along microvessels, the red cell velocity and intravascular pressure were simultaneously measured in the rat pial arterioles of 41-53 microm in diameter with a high temporal resolution by a laser-Doppler anemometer and a servo-null micropressure system. It was found that the velocity pulse preceded the pressure pulse in all the measured arterioles by 18.7-35.6 ms. The corresponding phase difference was 43.6+/-6.9 degrees (mean +/- SD), which is not statistically different from 45 degrees. The value is consistent with the phase difference predicted for the blood flow in microvessels with a small reflection coefficient at frequencies as low as the heart rate of the rats. The present results suggest that the upstream changes in blood flow are transmitted by the velocity pulse faster than by the pressure pulse in the microvasculature.

Animals↗
PubMed2005

[The electroporation effects of high power pulse microwave and electromagnetic pulse irradiation on the membranes of cardiomyocyte cells and the mechanism therein involved].

Though there is ongoing public concern on potential hazards and risk of electromagnetic radiation, the bioeffects mechanism of electromagnetic fields remains obscure. Heart is one of the organs susceptive to electromagnetic fields (EMF). This study was designed to assess the influence of high power pulse microwave and electromagnetic pulse irradiation on cardiomyocytes, to explore the critical mechanism of electromagnetic fields, and to explain the regular course of injury caused by exposure to pulse EMF. Cultured cardiomyocytes were irradiated by high power pulse microwave and electromagnetic pulse first, then a series of apparatus including atom force microscope, laser scanning confocal microscope and flow cytometer were used to examine the changes of cell membrane conformation, structure and function. After irradiation, the cardiomyocytes pulsated slower or stop, the cells conformation was abnormal, the cells viability declined, and the percentage of apoptosis and necrosis increased significantly (P< 0.01). The cell membrane had pores unequal in size, and lost its penetration character. The concentration of Na+, K+, Ca2+, Cl-, Mg2+, Ca2+ and P3+ in cell culture medium increased significantly (P< 0.01). and the concentration of Ca2+ in cells ([Ca2+]i) decreased significantly (P<0.01). The results indicated that cardiomyocytes are susceptible to non-ionizing radiation. Pulse electromagnetic field can induce cardiomyocytes electroporation, and can do great damage to cells conformation, structure and function. Electroporation is one of the most critical mechanisms to explain the athermal effects of electromagnetic radiation.

Animals↗
PubMed1990

Effects of pulse length and pulse strength on transfection by electroporation.

The relative importance of pulse field strength E and pulse length tau 1/2 (half decay time of an exponential decay pulse) on the stable transfection frequency for HeLa or HUT-78 cells was investigated. Cells were transfected with plasmids containing the promoter and drug resistant genes pRSVgpt or pRSVneo by electroporation. The stable transfection frequency was assayed using the marker rescue technique. The transfection frequency increases with increasing values of E tau 1/2. For a given pulse length, the transfection frequency is proportional to the power of the pulse (E2 tau 1/2). Pulses with half decay times of 2.2 to 4.6 ms appear to be more efficient than 0.275 to 0.31 ms for stable transfection of HeLa cells.

DNA↗
PubMed1988

The treatment of port-wine stains by the pulsed dye laser. Analysis of pulse duration and long-term therapy.

A flashlamp-pumped pulsed dye laser at 577 nm was evaluated in the treatment of port-wine stains. The degree of lesional lightening was compared following laser exposure with pulse durations of 20 and 360 microseconds. In addition, lesional therapy using the 360-microseconds pulse duration was evaluated for lightening and side effects following long-term patient observation and after repeated treatments of the same site. A total of 52 patients with port-wine stain were treated; their average age was 29 years, with eight patients less than 18 years, of whom 29 had comparative test site placement for the different pulse durations. Of these 29 patients, 25 demonstrated greater lightening at the 360-microseconds pulse duration test site. All 52 patients proceeded to receive full treatment placement with the 360-microseconds pulse duration, which resulted in an overall lightening of 42% after the initial treatment and 68% after re-treatment sessions. Forty-four percent of the patients had equal to or greater than 75% lesional lightening. Pretreatment anesthesia was unnecessary and only minimum posttreatment care was required. Mild adverse effects of epidermal change, depression, or pigmentary change appeared in only four cases and was limited to less than a 2% area in each of these lesions. These side effects did not recur when the lesions were re-treated at lower energy dosages. No posttreatment sclerosis or scarring appeared, even after multiple retreatment sessions to the same area, regardless of the anatomic location, color of the lesion, or age of the patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Separating field strength, temperature, and pulsing effects in pulsed field electrophoresis.

The utility of pulsed field electrophoresis for DNA sequencing is investigated. Previous studies have indicated a beneficial retardation of sequencing fragments when pulsed fields are employed. The interpretation of these results is complicated, however, by concomitant variations in electric field strength and/or temperature. Methods are presented here permitting discrimination of such mobility effects due to pulsing, field strength, and temperature. It is demonstrated that under the conditions employed here, observed mobility effects are due to electric field variations rather than pulsing. These conditions thus correspond to the low frequency/small molecule limit. The effect of temperature is estimated from the steady state solution to the heat conduction equation under appropriate boundary conditions. No temperature effect upon mobility is operative in the thin gel system employed, due to the high efficiency of heat transfer. However, it is shown that in conventional gel systems large temperature-related mobility effects can occur. These methods for dissecting and understanding mobility effects in pulsed field electrophoresis are expected to be of general utility.

Base Sequence↗
PubMedDate not supplied

The relationship between arterial pulse-wave velocity and pulse frequency at different pressures.

Pulse-wave velocity was measured in isolated canine common carotid arteries using sinusoidal frequency pulses of 1, 2, 5, 10, 15 and 20 Hz at 50, 100 and 150 mmHg. It was found that the pulse-wave velocity was independent of frequency and dependent on pressure. Using the Moens-Korteweg equation, the predicted pulse-wave velocity (y) was compared with measured pulse-wave velocity (x). A good correspondence was found (y = 1.063 x - 0.337, with a correlation coefficient of 0.963). The propagation velocity of the significant harmonic components of the pulsatile pressure waveform is the same for heart rates up to 120 beats/min.

Animals↗
PubMed1989

[Pulse oximetry--a non-invasive method for direct and continuous monitoring of oxygen saturation and pulse rate--comparative studies with blood gas analysis and hemoreflectometry in the dog, swine and sheep].

The use of pulse oximeters as a non-invasive, real time and online method for the continuous monitoring of oxygen saturation is discussed and compared to other methods like hemoreflectometry, and blood gas analysis. Analyses of linear regression show extraordinarily good correlations between all three monitoring systems. Pulse oximetry and hemoreflectometry on the one hand and blood gas analysis on the other hand sometimes show quite differing values of oxygen saturation. This phenomenon is due to the fact that the measuring methods are based on different working principles as well as it can be explained by the various hemoglobin-types. The pulse rate also measured by the pulse oximeter is nearly completely identical to the heart rate of the ECG. A slight temporal delay between the two acoustic signals is noticed and justified. Pulse oximetry seems to be superior to other oxygen monitoring systems because of its continuous noninvasive measuring technique.

Animals↗
PubMed1983

Transmission delays of different portions of the arterial pulse. A comparison between the indirect aortic and carotid pulse tracings.

The transmission delays of the upstroke and incisura of the arterial pulse were measured in 128 normal subjects, divided in three groups of increasing age, by comparing the timing of the indirect aortic arch pulse (recorded at the suprasternal notch) (SSN) and the indirect, right carotid tracing (CAR). In the total group, the mean delay of the upstroke was 24.4 msec while the mean delay of the incisura was 19 msec (P less than 0.005). This difference was maximal in the oldest age group and became non significant in the group of children under 12. At slow heart rate, this difference was greater than at a more rapid heart rate. The left ventricular ejection times (LVET), measured on the two pulses, showed a very close correlation (r = 0.96) but the LVET was significantly longer in the SSN tracing, especially in the older subjects. These data reveal that the incisura of the arterial pulse travels more rapidly than the upstroke, especially in older patients and at lower heart rates. The most likely explanation of this fact resides in the frequency-dependent influence of vascular reflections, which is more important with increasing age and slower heart rate. Thus, the transmission velocity along the arterial wall is higher for the higher harmonics of the pulse wave (incisura) than for the lower harmonics (upstroke).

Adolescent↗
PubMed1996

Effect of laser pulse repetition rate and pulse duration on mast cell number and degranulation.

BACKGROUND AND OBJECTIVE: Mast cell activation by low-level laser therapy (LLLT), leading to degranulation and the release of mediators, may be one of the mechanisms by which LLLT can accelerate tissue repair in mammals. The objective of this work, part of an investigation to determine the optimum parameters for increasing mast cell number and degranulation in injured skin, was to determine the effect of different pulsing frequencies of LLLT. STUDY DESIGN/MATERIALS AND METHODS: Partial-thickness wounds in anaesthetized adult male Wistar rats were irradiated immediately after injury with monochromatic coherent light (wavelength 820 nm) pulsed at either 2.5, 20, 292, or 20,000 Hz at an average power density of 800 mW/cm2 for 27 seconds; the energy density was 21.6 J/cm2. The effects on mast cell number and degranulation were assessed 2 hours post-treatment by counting the numbers of intact and degranulated mast cells in Carnoy-fixed, toluidine blue-stained, sections of irradiated and sham-irradiated wounds. RESULTS: The total number of mast cells was increased significantly (P < 0.05) by all the frequencies when compared to the sham-irradiated group, but there was no significant difference between frequencies (P > 0.05). However, although the number of degranulated mast cells was higher in all laser-treated wounds, in comparison with the sham-irradiated group, only the 20 Hz (pulse duration 45 ms) and 292 Hz (pulse duration 3 ms) frequencies were significantly effective (P < 0.05). CONCLUSION: Increase in mast cell number is not pulsing frequency dependent, whereas degranulation is.

Animals↗
PubMed1976

Rapid evaluation of many pulse echo system characteristics by use of a triggered pulse burst generator with exponential decay.

A pulse burst generator is utilized in which the pulses are triggered by the transmitter pulse of the ultrasound system being tested. The pulses are spaced the equivalent of every 2 mm in the body, and their amplitude decays with 0, 1.25, or 2.5 dB/cm over greater than a 50 dB dynamic range. By replacing the ultrasound transducer with the pulse generator, one can record quite easily the accuracy of depth gain compensation (DGC) and of distance measurements in A mode and B mode. If the DGC on the ultrasound unit can be turned to zero, the unit's A mode display characteristic and B mode gray scale curve can be determined rapidly and the receiver gain control or attenuator can be calibrated. Measurement of a receiver signal-to-noise ratio is possible, and more quantitative imaging should be facilitated as well.

Evaluation Studies as Topic↗
PubMed2005

Quantifying CBF with pulsed ASL: technical and pulse sequence factors.

We summarize here current methods for the quantification of CBF using pulsed arterial spin labeling (ASL) methods. Several technical issues related to CBF quantitation are described briefly, including transit delay, signal from larger arteries, radio frequency (RF) slice profiles, magnetization transfer, tagging efficiency, and tagging geometry. Many pulsed tagging schemes have been devised, which differ in the type of tag or control pulses, and which have various advantages and disadvantages for quantitation. Several other modifications are also available that can be implemented as modules in an ASL pulse sequence, such as varying the wash-in time to estimate the transit delay. Velocity-selective ASL (VS-ASL) uses a new type of pulse labeling in which inflowing arterial spins are tagged based on their velocity rather than their spatial location. In principle, this technique may allow ASL measurement of cerebral blood flow (CBF) that is insensitive to transit delays.

Arteries↗
PubMed1988

Pulsed CO2 laser tissue ablation: effect of tissue type and pulse duration on thermal damage.

Tissue removal by infrared lasers is accompanied by thermal damage to nonablated tissue. The extent of thermal damage can be controlled by a choice of laser wavelength, irradiance, and exposure duration. The effect of exposure duration has been studied in vivo by using CO2 lasers with pulse widths that vary from 2 microseconds to 50 msec. Pulse widths of 50 msec, typical of a shuttered, continuous-wave CO2 laser, produce damage regions 750 micron wide in normal guinea pig skin; the use of a 2-microseconds-long pulse reduced this damage zone to as little as 50 micron. Using 2-microseconds-long pulses, in vitro studies showed that the minimum zone of thermal damage varied significantly with tissue type. The thermal denaturation of these tissues has been studied and correlated with damage. The effect of denaturation temperature and pulse duration on the width of the damage zone is explained by a simple model.

Animals↗
PubMed2006

GABA-mediated echo duration selectivity of inferior collicular neurons of Eptesicus fuscus, determined with single pulses and pulse-echo pairs.

When insectivorous bats such as Eptesicus fuscus emit ultrasonic signals and analyze the returning echoes to hunt insects, duration selectivity of auditory neurons plays an important role in echo recognition. The success of prey capture indicates that they can effectively encode progressively shortened echo duration throughout the hunting process. The present study examines the echo duration selectivity of neurons in the central nucleus of the bat inferior colliculus (IC) under stimulation conditions of single pulses and pulse-echo (P-E) pairs. This study also examines the role of gamma-aminobutyric acid (GABA)ergic inhibition in shaping echo duration selectivity of IC neurons. The data obtained show that the echo duration selectivity of IC neurons is sharper when determined with P-E pairs than with single pulses. Echo duration selectivity also sharpens with shortening of pulse duration and P-E gap. Bicuculline application decreases and GABA application increases echo duration selectivity of IC neurons. The degree of change in echo duration selectivity progressively increases with shortening of pulse duration and P-E gap during bicuculline application while the opposite is observed during the GABA application. These data indicate that the GABAergic inhibition contributes to sharpening of echo duration selectivity of IC neurons and facilitates echo recognition by bats throughout different phases of hunting.

Acoustic Stimulation↗