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PubMed2004

Pulsed homodyne measurements of femtosecond squeezed pulses generated by single-pass parametric deamplification.

A new scheme is described for the generation of pulsed squeezed light by use of femtosecond pulses that have been parametrically deamplified through a single pass in a thin (100-microm) potassium niobate crystal with a significant deamplification of approximately -3 dB. The quantum noise of each pulse is registered in the time domain by single-shot homodyne detection operated with femtosecond pulses; the best squeezed quadrature variance was 1.87 dB below the shot-noise level. Such a scheme provides a basic resource for time-resolved quantum communication protocols.

Journal Article↗

PubMed2004

Pulse collisions in the stretched-pulse fiber laser.

We report the observation of a new regime of operation in the stretched-pulse fiber laser in which two groups of bound pulses travel in the cavity at different velocities. The pulse groups collide periodically and remain apparently unaltered after the collisions. The observed group-velocity difference is shown to exhibit a strong dependence on the time interval between the pulses in each bound state.

Journal Article↗

PubMed2005

Generation of high-contrast millijoule pulses by optical parametric chirped-pulse amplification in periodically poled KTiOPO4.

A new high-contrast, high-gain optical parametric chirped-pulse amplifier (OPCPA) architecture is demonstrated in periodically poled KTiOPO4 (PPKTP). This architecture overcomes parametric fluorescence contrast limitations of the OPCPA in periodically poled materials. The scheme is based on two passes of a single relay-imaged pump pulse and a free-propagating signal pulse through a 1.5 mm x 5 mm x 7.5 mm PPKTP crystal. The output energy of 1.2 mJ is generated at a center wavelength of 1053 nm by 24 mJ of pump energy. A prepulse contrast level of > 3 x 10(7) was measured with > 10(6) saturated gain in the amplifier. Amplified pulses were compressed to 200 fs. This simple and versatile concept requires only a modest pump energy from a commercial pump laser and represents a possible high-contrast front end for high-energy Nd:glass-based petawatt-class lasers.

Journal Article↗

PubMedDate not supplied

Transcranial electrical stimulator producing high amplitude pulses and pulse trains.

Transcranial electrical stimulation can be used for clinical investigations of the central nervous system and for monitoring of motor nerve tracts during surgical operations. We wished to reduce the pain involved with the transcranial electrical stimulation and to improve the usefulness of the method for monitoring during surgical operations. A dedicated transcranial electrical stimulator was designed having special features to reduce the pain sensation and the nerve blocking effect of anaesthetics. It provides constant current and constant voltage stimulation pulses with very short duration and high amplitude. The pulse length is adjustable in the range of 15 to 125 microseconds, while the maximum amplitude is 100 V and 1 A for voltage and current stimulation modes, respectively. Special features included high-repetition-rate pulse trains (50-2000 pulses s-1) and a three-electrode stimulation configuration. We suggest that the electrical transcranial stimulation has the potential to be a relatively painless method for routine clinical investigations and a reliable method for monitoring during surgery.

Amplifiers, Electronic↗

PubMed1992

[Reproducibility of the measurement of humeral artery diameter, velocity of carotido-femoral pulse wave and digital pulse wave in normal subjects].

The aim of this study was to assess the intra-observer reproducibility at short and medium term of three non-invasive methods of arterial measurement: in the same day eight volunteers underwent five successive measurements of brachial artery diameter by two dimensional pulsed Doppler of the carotido-femoral pulse wave velocity by a piezoelectric transducer. The measurements were repeated three times at two weeks' interval. The short term (same day) and medium term (after several weeks) reproducibility of the first two methods of measurement was good: 4.69 +/- 2.37%/4.24 +/- 1.90% and 4.09 +/- 1.16%/5.02 +/- 1.71% respectively for brachial artery diameter and carotido-femoral pulse wave velocity. The reproducibility of the method of measuring digital pulse wave velocity was 10.64 +/- 3.50%/11.62 +/- 4.25%, confirming the greater variability of this parameter. Our results with these noninvasive techniques indicate that they may be used to study the arterial system and could be clinically useful in the surveillance of hypertensive patients.

Adult↗

PubMed1982

Studies in brief-pulse electroconvulsive therapy: the voltage threshold, interpulse interval, and pulse polarity parameters.

Three studies of parameters of short-pulse ECT are reported: (i) voltage threshold, (ii) interpulse interval, an (iii) pulse polarity. Using a defined standard stimulus, voltage thresholds were found to vary from 110-250 V with a mean of 185 V. Some patients also required an increased number of pulses. The interpulse interval study demonstrated that intervals from 30 to 50 msec were successful in over 90% of the group. An interpulse interval of 30 msec was adopted as a standard treatment. The third study demonstrated no difference in efficiency of convulsion production when all positive, all negative, or alternating positive and negative pulse stimuli were applied.

Adult↗

PubMed1995

Preparation, manipulation, and pulse strategy for one-dimensional pulsed-field gel electrophoresis (ODPFGE).

The underlying principles for zero-integrated-field electrophoresis (ZIFE) pulses and more general forward-biased pulse schemes are reviewed for one-dimensional pulsed-field gel electrophoresis (ODPFGE) separations of large DNA molecules. Detailed descriptions of materials, preparation protocols, hardware requirements, and procedures are given. A variety of gel pictures for known yeast DNA markers are shown.

Algorithms↗

PubMed1991

Minimum pulse pressure and peripheral temperature needed for pulse oximetry during cardiac surgery with cardiopulmonary bypass.

The lowest values of pulse pressure (dPP) and peripheral temperature (Tp) associated with reliable readings from three different pulse oximeters (Biox Ohmeda 3700, Datex Satlite, and Nellcor N-200) were assessed, along with the ability of the pulse oximeters to work immediately before and after total cardiopulmonary bypass (CPB). The lowest mean dPP with a reliable O2 saturation reading was 13 mm Hg and the lowest mean Tp was 23.6 degrees C. The dPP needed for a reliable reading before total CPB did not differ significantly from that needed after total CPB. No significant differences in performance were found among the three oximeters during the study.

Adult↗

PubMed2001

Pulse pressure and aortic pulse wave are markers of cardiovascular risk in hypertensive populations.

BACKGROUND: Pulse pressure (PP) and aortic pulse wave velocity (PWV) are significant markers of cardiovascular risk, but a similar role for central wave reflections has never been investigated. PROCEDURES: To determine the factors influencing PP, PWV, and carotid wave reflections, a cohort of 1087 patients with essential hypertension either treated or untreated was studied cross-sectionally. Atherosclerotic alterations (AA) were defined on the basis of clinical events and PWV evaluated from an automatic device. The carotid amplification index (CAI), a quantitative estimation of the magnitude of central wave reflections, was measured noninvasively from pulse wave analysis using radial and carotid aplanation tonometry. RESULTS: In the overall population, age and mean arterial pressure represented 30.4%, 32.3%, and 5.6% of the variance of, respectively PP, PWV, and CAI. For the latter, body weight and heart rate represented 22.9% of variability. On the basis of logistic regression, AA were associated, in addition to age, plasma creatinine and HDL cholesterol levels, and tobacco consumption to three mechanical factors, increased PP, increased PWV, and low diastolic blood pressure, but not by CAI (adjusted odds ratio: 1.00; 95% confidence intervals: 0.99-1.01). CONCLUSION: In cross-sectional hypertensive populations, PP and PWV, but not CAI, are significantly and independently associated with cardiovascular amplications.

Aged↗

PubMed2006

Pulse-wave morphology and pulse-wave velocity in healthy human volunteers: examination conditions.

OBJECTIVE: Applanation tonometry for pulse-wave analysis (PWA) and determination of pulse-wave velocity (PWV) is a non-invasive method for assessment of the central aortic pressure waveform and indices of arterial stiffness. The objective of this study was to examine the influence of eating and smoking on PWA and PWV measurements in order to establish standard examination conditions. Furthermore, intra- and interobserver reproducibility and the effects of varying the site of measurements were observed. MATERIAL AND METHODS: Duplicate measurements of the radial pressure waveform and of the brachial and aortic PWV on the right and left side of the body were recorded in 23 healthy subjects by two trained observers. Measurements were performed in the fasting state and 3 h after a high-calorie meal, and before and 1 h after smoking a cigarette. RESULTS: Intake of a high-calorie meal as well as smoking caused significant changes in both PWA and PWV parameters and an inter-arm difference was observed. Intra- and interobserver reproducibility was good. CONCLUSIONS: Pulse-wave measurements by applanation tonometry should be undertaken in the same arm during fasting and smoking abstinence.

Adult↗

PubMed2006

Pulse wave analysis and pulse wave velocity: a review of blood pressure interpretation 100 years after Korotkov.

The pulsatile component of blood pressure (ie, pulse pressure) has received considerable attention as an important risk factor for cardiovascular disease. In particular, central blood pressure measurements in the ascending aorta or in the carotid artery are expected to be more useful than conventional brachial pressure measurements for predicting cardiovascular events because central pressure, not the brachial pressure, is the pressure that target organs encounter. Due to wave reflection, the blood pressure in the upper limb does not represent the central blood pressure; therefore, leading researchers have enthusiastically promoted a noninvasive method of measuring central blood pressure and the resulting aortic stiffness. Until now, there has been an increasing body of evidence to support the accuracy and superiority of central blood pressure measurements as well as the assessment of aortic properties over classical brachial pressure measurements. In this review, the information regarding these "central" indices derived from 2 main methods, namely "pulse wave analysis" and "pulse wave velocity", for the application of central blood pressure measurements and arterial stiffness to clinical study and practice, has been summarized.

Aorta↗

PubMedDate not supplied

Pulse volume recordings in outer ear canal in pulse synchronous tinnitus. A comparison between ears with Glomus tumour, serous otitis media, and normal ears.

With the aid of a volume flowmeter it is possible to record pulse synchromous volumetric changes in the outer ear canal. In 7 ears with glomus tumour in the tympanic cavity and in 5 with serous otitis media, such changes were larger than in 125 persons with a normal middle ear. By changing the ambient pressure in a pressure chamber and instructing the patients not to swallow, the drum can be pushed inward or outward. In all the cases of glomus tumour studied the pulse volumetric change was considerably affected when the drum was pushed inward or outward. In the normal patients the change was no change at all. This means that the pulse volume changes in normals are generated mainly by the vessels in the outer ear canal.

Adolescent↗

PubMed1999

[Clinical importance of fetal pulse oximetry. I. Methodological evaluation. Multicenter study. French Study Group on Oximetry of Fetal Pulse].

OBJECTIVE: To evaluate the feasibility of intrapartum fetal pulse oximetry, the distribution of fetal oxygen saturation values, and the relation with the neonatal outcome in a population with an abnormal fetal heart rate (FHR). STUDY DESIGN: A prospective multicenter observational study, from June 1994 to November 1995. Fetal oxygen saturation was continuously recorded using a Nellcor N-400 fetal pulse oximeter in case of abnormal FHR during labor. Simultaneous readings of fetal oxygen saturation and of fetal blood analysis (FBA) were obtained at inclusion and before birth. Feasibility, adverse effects, distribution of fetal oxygen saturation values and relation with neonatal outcome were assessed. RESULTS: 74 patients were included. From 172 attempted sensor placements, the procedure was impossible in three cases and fetal oxygen saturation values were obtained in 164 cases (95.3%). Physicians considered sensor placement an easier task than FBA attempt (easy in 87.5% vs 78.9% for FBA, p = 0.03). The mean reliable signal time (+/- SD) was 64.7 +/- 32% during the first stage. There were no serious adverse effects in the study population. The mean fetal oxygen saturation during the first stage of labor was 42.2 +/- 8.0% (10th-90th centile range: 30-53%). Fetal oxygen saturation was significantly correlated with scalp pH (r = 0.29; p = 0.01) but not with neonatal umbilical artery pH or gas values. There was a significant association between a low fetal oxygen saturation (< 30%) and a poor neonatal condition. CONCLUSION: The feasibility of fetal pulse oximetry is satisfactory in clinical practice. It is easy to use and provides a fair rate of recorded values, even in a population with suspicion of fetal distress. A low fetal oxygen saturation is significantly associated with an abnormal neonatal outcome.

Adult↗

PubMedDate not supplied

[The "Pulse" computer-based analyzer for measuring the pulse-wave and electric cardiac activity].

The paper deals with a device designed for the express-examination of the cardiac-vascular system through reading and processing the synchronously incoming electrocardiosignal and pulse-wave. The equipment is convenient for monitoring intraoperatively the functions of pacemaker due to its ability to select an optimal regimen not only for ECG but also for the pulse-wave. The new method of registering the pulse-wave by a miniature fiber-optic pressure sensor is described.

Cardiovascular Physiological Phenomena↗

PubMed1986

[Correlation of LH and prolactin pulses in normoprolactinemic women with ovulatory disturbances and variation of LH and FSH pulses and secreting capacity by administration of bromocriptine in the same cases].

The difference between prolactin (PRL) basal levels on separate days in the 6 normoprolactinemic women--one case with an anovular cycle and 5 cases with 1 degree amenorrhea--among 14 normoprolactinemic women with ovulatory disturbances, showed significantly variation over 13 ng/ml within the normal range of the PRL basal level. PRL pulse frequencies of the same cases from 0900 h. to 1400 h. increased slightly compared with follicular phase. At the same time, the PRL pulse amplitudes were significantly higher than in the follicular phase but significantly lower than the PRL pulse amplitudes in hyperprolactinemic women. The net increase in PRL to TRH in the 6 cases was over 100 ng/ml. When the PRL net increase to TRH was over 100 ng/ml in normoprolactinemic women with ovulatory disturbances, the case is regarded as latent hyperprolactinemia. And 1 or 2 may be latent hyperprolactinemic syndrome. The LH/FSH basal level and delta LH/delta FSH to LH-RH before administration of bromocriptine increased in these cases compared with the follicular phase. During the administration of bromocriptine, the ratios decreased and approached the ratio in the follicular phase. The effect of clomid was improved by increased E2 in these cases.

Amenorrhea↗

PubMed2004

Treatment of leg veins with the long pulse dye laser using variable pulse durations and energy fluences.

BACKGROUND AND OBJECTIVES: Attempts at using the pulsed dye laser (PDL) operating at 585 nm wavelength and 0.45 milliseconds pulse duration to treat leg veins have been notably unsuccessful. The aim of this study is to evaluate the efficacy and complications of the 595 nm long PDL in the treatment of leg veins. STUDY DESIGN/PATIENTS AND METHODS: Fourteen patients with 38 lesions were treated using a long PDL equipped with a cryogen spray cooling (CSC) device. Variable pulse durations ranging from 1.5 to 20 milliseconds and energy fluences from 10 to 20 J/cm2 were utilized depending on the size of treated vessels. All patients received two laser treatments at an interval of 2 months. RESULTS: Of patients with veins type 1A and type 1, 6 (100%) and 3 (13%) had complete clearing, respectively. Of patients with veins type 1 and type 2, 18 (78.3%) and 2 (22.2%) lesions showed excellent response, respectively. Hyperpigmentation was the only observed complication lasting several months in 57.9% of treated sites. CONCLUSIONS: The long PDL operating at 595 nm is a safe and effective treatment for leg veins, especially in type 1A and type1 vessels.

Adult↗

PubMed1997

Optimization of the water-PRESS pulse sequence and its integration into pulse sequences for studying biological macromolecules.

In this paper, the recently developed "Water-PRESS" method of water suppression [W. .S. Price and Y. Arata (1996), J. Magn. Reson. B 112, 190] in which homospoil pulses are used to manipulate the effects of radiation damping on the water resonance and thereby selectively alter the effective relaxation times of the water resonance with respect to the solute (e.g., biological macromolecules) resonances is further developed and applied. In the present work, methods for optimization in terms of degree of water suppression and in temporal terms (important for the application of Water-PRESS to multidimensional experiments) are considered so that recycle delays of less than 2.3 s (including the acquisition time) are possible. Also, a simple modification which allows the observation of solute resonances with relaxation times similar to that of the water resonance is presented. Finally, the inclusion into more complicated pulse sequences is also discussed. Experimental examples using aqueous samples of lysozyme and immunoglobulin are given. Compared to most other NMR water suppression techniques, this method is extremely simple to implement and optimize and does not require accurately calibrated RF pulses or perfect lineshape.

Animals↗

PubMed1990

Biphasic voltage relaxation pattern observed in cells of Eremosphaera viridis after injection of charge-pulses of short duration: detection of tip clogging of intracellular microelectrodes by charge-pulse technique.

Charge pulse experiments performed on the peat-bog alga Eremosphaera viridis revealed an unusual voltage relaxation behaviour. Injection of charge pulses of 1 microseconds duration resulted in an immediate charging of the membranes (time constant of the order of 40 ns). Nevertheless, the potential-measuring microelectrode recorded an exponential increase in membrane voltage with a time constant of about 1.3 ms. The maximum voltage value was recorded after about 3 ms, followed by an exponential decay with a time constant of about 9.6 ms. This biphasic time course was independent of the amplitude of the injected charge and of the location of the impaled microelectrodes in the vacuole. Centrifuged cells in which the chloroplasts and the other organelles were pelleted in one part of the cells showed the same electrical response. Electrical breakdown of the cell membranes resulted in the disappearance of the biphasic voltage response. In this case only the decaying relaxation process could be recorded with a time constant of 3 ms. After resealing of the membranes the original biphasic relaxation response was restored. Increasing concentrations of KCl in the bathing medium reduced both time constants almost correspondingly. The experimental findings were evaluated with an electrical equivalent circuit. Theoretical analysis with reference to the experimental data suggested that the delayed voltage response of the potential-recording electrode resulted from a membrane seal across the tip of this electrode. The resistance of this seal was calculated to be about 400 M omega. The specific resistances and capacitances of tonoplast and plasmalemma membranes were calculated from the decaying part of the biphasic relaxation curves. The average values were found to be 2.58 omega.m2 and 5 mF.m-2. The investigations reported here suggest that charge pulse experiments can be generally used for the detection of membrane and cytoplasmic material clogging of the tip of intracellular microelectrodes, a problem with which most electrophysiologists are faced when interpreting data obtained from impaled microelectrodes.

Cell Membrane↗