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At least 253 records · Page 14Linked to original sources
PubMed2004

Chirped-pulse oscillators: a route to high-power femtosecond pulses without external amplification.

We demonstrate a Kerr-lens mode-locked Ti:sapphire oscillator that generates 130-nJ, 26-fs and 220-nJ, 30-fs pulses at a repetition rate of 11 MHz. The generation of stable broadband, high-energy pulses from an extended-cavity oscillator is achieved by the use of chirped multilayer mirrors to produce a small net positive dispersion over a broad spectral range. The resultant chirped picosecond pulses are compressed by a dispersive delay line that is external to the laser cavity. The demonstrated peak powers, in excess of 5 MW, are to our knowledge the highest ever achieved from a cw-pumped laser and are expected to be scalable to tens of megawatts by an increase in the pump power and (or) a decrease in the repetition rate. The demonstrated source permits micromachining of any materials under relaxed focusing conditions.

Journal Article↗
PubMed2005

Double chirped-pulse-amplification laser: a way to clean pulses temporally.

We demonstrate a double chirped-pulse-amplification (CPA) Ti: sapphire laser system that includes two CPA stages with intermediate nonlinear temporal pulse filtering. The method makes it possible to reduce substantially the background of amplified spontaneous emission (ASE), including prepulses and postpulses. An ASE temporal contrast of 10(10) was demonstrated at 20 mJ of output energy and 50-fs pulse duration. The demonstrated scheme is applicable to petawatt power-level laser systems.

Journal Article↗
PubMed2006

Stationary rescaled pulse in dispersion-decreasing fiber for pedestal-free pulse compression.

By using the concept of a stationary rescaled pulse (SRP), we analyze an adiabatic soliton compression system based on dispersion-decreasing fiber (DDF). We show that a SRP can exist in a DDF with a linearly decreasing dispersion profile and that the SRP resembles a linearly chirped sech2 pulse. According to the analysis, we show numerically that pedestal-free pulse compression is possible by using the SRP.

Journal Article↗
PubMed2006

Efficient reflection grisms for pulse compression and dispersion compensation of femtosecond pulses.

Efficient reflection grisms for pulse-compression and material-dispersion compensation have been designed and demonstrated in a 40 fs, 300 microJ, 5 kHz downchirped pulse amplification system for the first time to our knowledge. A grism design for 800 nm femtosecond laser pulse dispersion compensation applications is realized by using standard, commercial diffraction gratings.

Equipment Design↗
PubMed2005

Pulse energy dependence of subcellular dissection by femtosecond laser pulses.

Precise dissection of cells with ultrashort laser pulses requires a clear understanding of how the onset and extent of ablation (i.e., the removal of material) depends on pulse energy. We carried out a systematic study of the energy dependence of the plasma-mediated ablation of fluorescently-labeled subcellular structures in the cytoskeleton and nuclei of fixed endothelial cells using femtosecond, near-infrared laser pulses focused through a high-numerical aperture objective lens (1.4 NA). We find that the energy threshold for photobleaching lies between 0.9 and 1.7 nJ. By comparing the changes in fluorescence with the actual material loss determined by electron microscopy, we find that the threshold for true material ablation is about 20% higher than the photobleaching threshold. This information makes it possible to use the fluorescence to determine the onset of true material ablation without resorting to electron microscopy. We confirm the precision of this technique by severing a single microtubule without disrupting the neighboring microtubules, less than 1 micrometer away.

Actins↗
PubMed2002

Study of operational aspects of pulse polio booths during Intensified Pulse Polio Immunisation Campaign in assembly segments of East Delhi.

The study was undertaken with the objective of observing operational aspects of 609 pulse polio booths established during Intensified Pulse Polio Campaign in East Delhi on National Immunisation Days (NID) during 2001-2002 through well designed format. The average number of persons present on duty at polio booths was 3.73 against a recommendation of 4 per booth. All the booths had vaccine carriers but some of them were not following the guidelines laid for maintaining the cold chain. One sixth "(15.4%)" of the booths needed fresh supplies of vaccine carrier. There is need for deployment of motivated trained manpower at polio booths to ensure the success of Pulse Polio Campaign. Maintenance of cold chain and quality assurance of vaccine administered to children in the field remain a challenge. More than half (55.7%) booths did not have any volunteer. Absence of volunteers from the community in more than half of the booths warrant for strengthening the linkages between the governmental agencies and the community.

Evaluation Studies as Topic↗
PubMed2002

Mitral inflow and mitral annular motion velocities in patients with mitral annular calcification: evaluation by pulsed Doppler echocardiography and pulsed Doppler tissue imaging.

AIMS: We evaluated the relationship between the mitral inflow velocities by pulsed Doppler echocardiography and mitral annular motion velocities by pulsed Doppler tissue imaging in patients with mitral annular calcification. METHODS AND RESULTS: Fifty-three patients with mitral annular calcification were divided into two groups: severe mitral annular calcification (n=15, mitral annular calcification bigger than or equal 5mm in width) and mild mitral annular calcification (n=38, mitral annular calcification <5mm in width). In addition, 20 patients with hypertensive heart disease (HHD group) and mild left ventricular hypertrophy but no mitral annular calcification and 30 normal individuals (normal group) were studied. The early diastolic mitral inflow velocity (E) was higher in the severe mitral annular calcification group (0.75+/-0.26 m/s) than in the HHD and normal groups (mild mitral annular calcification, 0.65+/-0.21; HHD, 0.57+/-0.24; normal, 0.55+/-0.15m/s), and the late diastolic mitral inflow velocity (A) was higher in the severe mitral annular calcification group (1.24+/-0.23 m/s) than in the other three groups (mild mitral annular calcification, 0.96+/-0.20; HHD, 0.84+/-0.23; normal, 0.75+/-0.13 m/s). In contrast, the early and late diastolic annular velocities (Ea, Aa) were lower in the severe mitral annular calcification group (Ea: 5.7+/-2.2; Aa: 11.9+/-4.4 cm/s) than in the other three groups (Ea: mild mitral annular calcification, 8.3+/-2.5; HHD, 7.7+/-2.2; normal, 9.0+/-1.8 cm/s; Aa: mild mitral annular calcification, 14.2+/-4.1; HHD, 14.3+/-2.8; normal, 14.2+/-2.1cm/s). Mitral valve area was smaller in the severe mitral annular calcification group (2.6+/-1.0 cm(2)) than in the other three groups (mild mitral annular calcification, 3.1+/-0.7; HHD, 4.1+/-0.7; normal, 4.2+/-0.9 cm(2)). In the mitral annular calcification and normal groups, the A correlated inversely with mitral valve area (r=-0.67, P<0.01) and directly with severity of mitral annular calcification (r=0.65, P<0.01), and the Ea correlated inversely with left ventricular wall thickness (r=-0.37, P<0.01) and severity of mitral annular calcification (r=-0.45, P<0.01). CONCLUSION: Patients with severe mitral annular calcification have higher mitral inflow velocities due to mitral annular restriction and lower mitral annular velocities caused by decreased mitral annular motion and abnormal left ventricular relaxation.

Aged↗
PubMed1985

Effects of threat of shock and control over shock on finger pulse volume, pulse rate and systolic blood pressure.

Previous research has evaluated finger pulse volume (FPV) as a psychophysiological measure and found it to reflect anxiety, orienting, effort and anger. Controllable versus uncontrollable threats have been found to have different effects on cardiovascular parameters, including pulse rate (PR) and systolic blood pressure (SBP). To date, no studies have compared the effects of such coping efforts on FPV with their effects on PR and SBP. The present study examined the response of PR, SBP and FPV to conditions of controllable shock, uncontrollable shock and no shock. As expected, SBP and PR measures were elevated in the controllable as compared to uncontrollable shock conditions, replicating previous work on cardiovascular responses to coping demands. In contrast, FPV was sensitive to the threat of shock, but did not differ as a function of the coping demands of the task. The findings were discussed in terms of the interpretation of FPV as a psychophysiological measure.

Adolescent↗
PubMed2006

Interaction between pulse wave velocity, augmentation index, pulse pressure and left ventricular function in chronic heart failure.

Pulse wave velocity (PWV), the carotid augmentation index (AIx), and pulse pressure (PP) may be prognostic factors in heart failure, but the possible influence of the ejection fraction (EF) and other simple haemodynamic variables on them has not been investigated in this setting. Noninvasive methods were used to measure carotid-radial (CR), carotid-femoral (CF) PWV and AIx, and brachial PP, in 135 consecutive patients with stable symptomatic chronic heart failure. The patients were divided into two groups, with preserved (>or=40%) or reduced (<40%) EF. CF-PWV, AIx and PP were lower in the decreased EF group (8.85+/-2.77 versus 10.60+/-2.75 m/s, P<0.001; 121+/-21 versus 132+/-24, P=0.009 and 41+/-19 versus 67+/-17 mmHg, P<0.001), but CR-PWV values were similar regardless of the EF status. These results were not modified after adjustment for age and sex. Multiple regression analysis showed that AIx and PP were systematically related to time domain parameters (heart rate or ejection duration) and EF, whatever the group. CF-PWV was weakly related to time domain values and unrelated to mean blood pressure (BP) or EF in the preserved EF group, whereas it was related to both mean BP and EF in the low EF group. In conclusion, whatever the EF level, PP and AIx were strongly modulated in the time domain, by pressure and by the EF level. The same relationships were found with CF-PWV, but only in the reduced EF group. Whether CF-PWV is the best prognostic factor in patients with 'diastolic' heart failure must be confirmed in a prospective study.

Aged↗
PubMedDate not supplied

Increased pulse wave velocity and shortened pulse wave transmission time in hypertension and aging.

We measured pulse wave velocity (PWV) and pulse transmission time (PTT) in 29 patients with hypertension, ranging in age from 37 to 73 years, in a series of 36 normal subjects with the same age range, and in an additional series of 44 normal subjects aged 18-35 years. PWV increases linearly with age for both normal subjects and patients with hypertension, with a corresponding significant decrease in PTT. There was a statistically highly significant (p < 0.001) increase in PWV in hypertension at all ages examined. The present simple noninvasive methods may be useful when evaluating risk factors for atherosclerosis and when evaluating response to therapeutic intervention.

Adolescent↗
PubMed1988

Wideband external pulse recording during cuff deflation: a new technique for evaluation of the arterial pressure pulse and measurement of blood pressure.

Analysis of the external brachial pulse recorded during standard blood pressure cuff deflation with use of a transducer with a wide frequency response has revealed a reproducible pattern with three distinct components that we have labeled K1, K2, and K3. K1 is a low-amplitude, low-frequency signal that is present with cuff pressures above systolic pressure. K2 is a triphasic signal appearing at systolic pressure and disappearing at diastolic pressure, which approximately corresponds to the audible Korotkoff sound. K3 appears with cuff pressure between systolic and diastolic pressure and continues to be present below diastolic pressure. Intra-arterial pressure recordings made with a high-fidelity Millar catheter-tip manometer revealed K2 and K3 analogs. K3 resembles the intra-arterial pressure waveform and when calibrated according to the pulse pressure, noninvasive dK3/dt determinations correlated well with intra-arterial dP/dt measurements. The appearance/disappearance property of K2 was designated as the "K2 algorithm" and represents a new, objective noninvasive method for measurement of blood pressure. The K2 algorithm compares favorably with intra-arterial measurements, is more accurate than the auscultatory technique, and may be especially useful in clinical situations in which the auscultatory technique does not work well.

Adolescent↗
PubMed2001

Effect of cilnidipine on left ventricular diastolic function in hypertensive patients as assessed by pulsed Doppler echocardiography and pulsed tissue Doppler imaging.

The purpose of the present study was to examine the mechanisms of improvement in left ventricular (LV) diastolic function in hypertensive patients treated with cilnidipine, a new and unique calcium antagonist that has both L-type and N-type voltage-dependent calcium channel blocking actions, using pulsed Doppler echocardiography and pulsed tissue Doppler imaging. The study comprised 35 untreated patients with essential hypertension (19 men and 16 women; mean age 65+/-10 years). The peak early diastolic and atrial systolic transmitral flow velocities (E and A, respectively) and their ratio (E/A), and the peak early diastolic and atrial systolic motion velocities (Ew and Aw, respectively) of the LV posterior wall and their ratio (Ew/Aw) were determined in all patients before and after 1, 3 and 6 months on cilnidipine (10 mg/day). One month: Systolic and diastolic blood pressures were significantly decreased. E and E/A were significantly increased, whereas there were no significant changes in Ew and Ew/Aw. Three months: Ew and Ew/Aw were significantly increased compared to those before and 1 month after cilnidipine. Six months: E and E/A were significantly increased compared with before and 3 months after cilnidipine, and Ew and Ew/Aw were significantly increased compared with before cilnidipine. Moreover, the LV mass index was significantly decreased compared to that before cilnidipine. In summary, changes in LV diastolic performance in patients with essential hypertension following cilnidipine treatment were biphasic with an initial increase in early diastolic transmitral flow velocity and a later increase in early diastolic LV wall motion velocity. The initial and later changes can be related to an acute change in afterload and a later improvement in LV relaxation.

Aged↗
PubMed2003

The relationship between pulse wave velocity and pulse pressure in Chinese patients with essential hypertension.

Aortic pulse wave velocity (PWV) is a significant and independent predictor of cardiovascular disease in hypertensive subjects and in patients with end-stage renal disease, but there have been few studies on PWV in Chinese patients with essential hypertension. In this cross-sectional study, we investigated 3,156 consecutive patients (mean age: 53.7 +/- 11.58 years) of the Hypertension Division of Ruijin Hospital in Shanghai. Together with sphygmomanometric blood pressure measurements, aortic PWV was measured using a validated automatic device. PWV in patients with pulse pressure (PP) > or = 60 mmHg was significantly greater than that in patients with PP < 60 mmHg (p < 0.01). PP and PWV were positively related to age (PP: r = 0.396, p = 0.001; PWV: r = 0.531, p = 0.001). After adjustment by age and heart rate, PWV was still closely related to PP (r = 0.249, p = 0.001). At any given systolic blood pressure (SBP), PWV significantly decreased with the increase of diastolic blood pressure (DBP), whereas at any given DBP there was a significant increase of PWV with the increase of SBP. In conclusion, PWV was the major determinant of PP, and was highest in Chinese patients with isolated systolic hypertension, followed by those with systolic and diastolic hypertension, isolated diastolic hypertension, and normal blood pressure.

Adult↗
PubMed1999

[A child of microscopic polyarteritis nodosa effectively treated with intravenous methylprednisolone pulses and serial cyclophosphamide pulse therapy].

Microscopic polyarteritis nodosa (mPAN) is a rare disorder in pediatric field of systemic small vessel vasculitis, and affects skin and musculoskeletal system accompanied by progressive necrotizing glomerulonephritis. We described here a 15-year-old boy with positive anti-neutrophil cytoplasmic antibody (MPO-ANCA) and severe mPAN, who was effectively treated with intravenous methylprednisolone pulse therapy followed by monthly cyclophosphamide pulses for 1 year. The histologic examination of renal biopsy specimen showed a severely desolated disease characterized by fibrinoid necrosis, crescent formation of most glomeruli and interstitial infiltration of inflammatory cells. The elevated titers of MPO-ANCA were useful markers for diagnosis, and the serial determinations of the antibody titers were indicative of disease activity. Moreover, dramatic clinical improvement after the induction of the combinatorial therapy and the disappearance of MPO-ANCA was correlated in the disease course. In this report, the serial determination of MPO-ANCA constituted a useful diagnostic tool and a sensitive marker of disease activity.

Adolescent↗
PubMed2003

Different influences on central and peripheral pulse pressure, aortic wave reflections and pulse wave velocity of three different types of antihypertensive drugs.

OBJECTIVE: To evaluate in hypertensive patients (pts) with similar peripheral blood pressure (BP) whether different antihypertensive treatments have different influences on aortic stiffness, aortic central pressures and aortic wave reflections. METHODS: In a cross-over study 41 nondiabetic hypertensives (21 women, age 35-60 yrs) were evaluated after stabilized (> 4 months) antihypertensive treatment and with casual BP between 130/80 and 160/95 mmHg. Patients were divided into 3 groups: Group I--12 pts all medicated with beta-blockers; Group II--14 pts all medicated with calcium channel blockers; Group III--15 pts all medicated with either angiotensin-converting enzyme inhibitors (ACEIs) (n = 8) or angiotensin II receptor blockers (ARBs) (n = 7). We evaluated casual BP and carotid-femoral pulse wave velocity (PWV). Systolic blood pressure (SBP) and pulse pressure (PP), left ventricular ejection duration (LVED), augmentation pressure (delta P) and augmentation index (AI%) in the aorta (a measure of aortic wave reflection), derived using radial and carotid applantation tonometry, were measured. Data are means + SEM. RESULTS: For similar casual peripheral BP values, group III vs. group I showed lower (p < 0.05) values of: aortic stiffness--PWV (10.3 +/- 0.2 vs. 11.2 +/- 0.3 m/s), central PP (48 +/- 2 vs. 55 +/- 2 mmHg), delta TP (11 +/- 3 vs. 21 +/- 3 mmHg), LVED (297 +/- 5 vs. 319 +/- 8 ms), AI% (22 +/- 4 vs. 39 +/- 3%), suggesting reduced vascular tone in the arteries and greater brachial-aortic PP amplification. Data in group II did not differ significantly from the other two groups. CONCLUSIONS: Independently of casual BP values, the three classes of antihypertensive drugs appear to have different influences on aortic stiffness, central pressures and aortic wave reflections, ACEIs or ARBs appearing to exhibit a more favorable profile.

Adult↗
PubMed2005

[The assessment of arteriolosclerosis by serum lipids data, and carotid ultrasonography and pulse wave velocity, and its evaluation as a tool for preventive medicine: II. Carotid ultrasonography and pulse wave velocity for hyperlipemia and diabetes mellitus].

We studied the test results of carotid ultrasonography and pulse wave velocity against a sample of hyperlipemia and diabetes mellitus. Sixty four hyperlipemia samples (HL), 85 diabetes mellitus samples (DS), and 27 complicated samples (CS) were compared with 56 healthy samples (HS). Hyperlipemia samples were selected from cholesterol under 300 mg/dl, and neutral fat under 300 mg/dl. Diabetes mellitus samples were selected from fasting plasma glucose (FBS) under 200 mg/dl. Samples from severe conditions with various disease were excluded. Ratio over 1.1 mm intima-media thickness (IMT) was 0% in HS, 48% in HL, 40% in DS and 33% in CS. PWV value was max 1896cm/s in CS. There was no significant correlation within IMT, serum lipid(Total Cholesterol, Neutral Fat, HDL-Cholesterol, LDL-Cholesterol) and FBS. For early treatment or accurate diagnosis of arteriosclerosis in hyperlipemia or diabetes mellitus patients, who are at high risk of developing arteriosclerosis, to vital function tests (carotid ultrasonography and pulse wave velocity) should be performed, in addition to normal blood tests.

Adult↗