Wide Pulse Research Articles

Fresnel transform phase retrieval from magnitude.

This report presents a generalized projection method for recovering the phase of a finite support, two-dimensional signal from knowledge of its magnitude in the spatial position and Fresnel transform domains. We establish the uniqueness of sampled monochromatic scalar field phase given Fresnel transform magnitude and finite region of support constraints for complex signals. We derive an optimally relaxed version of the algorithm resulting in a significant reduction in the number of iterations needed to obtain useful results. An advantage of using the Fresnel transform (as opposed to Fourier) for measurement is that the shift-invariance of the transform operator implies retention of object location information in the transformed image magnitude. As a practical application in the context of ultrasound beam measurement we discuss the determination of small optical phase shifts from near field optical intensity distributions. Experimental data are used to reconstruct the phase shape of an optical field immediately after propagating through a wide bandwidth ultrasonic pulse. The phase of each point on the optical wavefront is proportional to the ray sum of pressure through the ultrasound pulse (assuming low ultrasonic intensity). An entire pressure field was reconstructed in three dimensions and compared with a calibrated hydrophone measurement. The comparison is excellent, demonstrating that the phase retrieval is quantitative.

Pulse pressure is an independent risk factor of cardiovascular disease in renal transplant patients

Elevated pulse pressure in the general population has been shown to be associated with cardiovascular disease, which is the main cause of death in renal transplant patients. We investigated the effects that a wide pulse pressure has on cardiovascular disease after renal transplantation in a cohort of 532 transplant patients with functioning grafts for more than one year. Patients were classified into two groups depending on whether the one-year pulse pressure was less than or greater than 65 mm Hg. We analyzed patient survival, posttransplant cardiovascular disease and principle causes of death. Five- and ten-year patient survival were lower among the group with higher pulse pressures. The main cause of death was vascular disease in both groups. The presence of posttransplant cardiovascular disease was higher among the group with higher pulse pressures ( RR = 1.73). In addition, the incidence of an elevated pulse pressure was directly associated with recipient age and posttransplant diabetes mellitus. In conclusion, pulse pressure represents an independent risk factor for increased cardiovascular morbidity and mortality in renal transplant patients.

Cases from the Osler Medical Service at Johns Hopkins University

Presenting features A 53-year-old African American woman with a past medical history of menorrhagia was admitted to The Johns Hopkins Hospital for dyspnea that had worsened over the past several months. During this time, she noticed increasing breathlessness with activity, as well as occasional dark stools and a craving for ice chips. Initially, she had dyspnea with ambulation, but in the weeks leading up to admission she began to struggle with activities of daily living, including dressing herself and brushing her hair. By the day of admission, she complained of shortness of breath at rest. She denied fever, chest discomfort, orthopnea, paroxysmal nocturnal dyspnea, presyncope, syncope, hematemesis, or bright red blood per rectum. On physical examination, the patient appeared dyspneic and fatigued. She was tachycardic with a wide pulse pressure and bounding peripheral pulses. She was not orthostatic. There was prominent conjunctival pallor. Her precordium was hyperdynamic. The lungs were clear to auscultation without rales or fine inspiratory crackles. Her nail beds were normal, but palmar creases were not seen on her hands. She had 2+ bilateral lower extremity pitting edema up to her thighs. Rectal examination revealed guaiac-negative stool. Laboratory analysis revealed the following: hemoglobin, 2.7 g/dL; hematocrit, 11%; mean corpuscular volume, 62.3 fL; red cell distribution width, 24.8%; absolute reticulocyte count, 37.6 K/mm 3; and albumin, 3.0 g/dL. The patient's serum iron level was 14 μg/dL and her saturation iron was 3%, consistent with iron deficiency anemia. A peripheral blood smear showed microcytosis, anisocytosis, and hypochromia. Serum levels of aminotransferases, thyroid-stimulating hormone, vitamin B 12, folate, haptoglobin, lactate dehydrogenase, and antiendomysial antibody were normal, as were CD59 expression and a thalassemia screen. A chest radiograph revealed clear lung fields without infiltrates, and an electrocardiogram showed normal sinus rhythm without low voltage. Echocardiography revealed a hyperdynamic left ventricle with an ejection fraction of 75%, consistent with high output. What is the diagnosis?

Benefits of blood pressure reduction in elderly patients.

Hypertension in the elderly is characterized principally by increased systolic blood pressure (SBP). Consequently, isolated systolic hypertension (ISH) is the most common subtype in this population. The major haemodynamic determinant underlying ISH is increased large-artery stiffness. This is expressed as an increase in SBP and decrease in diastolic blood pressure (DBP), leading to widening pulse pressure. Epidemiological studies show that ISH and increased pulse pressure in the elderly constitute independent cardiovascular risk factors and may be more robust in predicting the adverse cardiovascular sequelae of hypertension than elevated DBP alone. Reducing high blood pressure (> 140/90 mmHg), including ISH (SBP > 140 mmHg, DBP < 90 mmHg), with conventional and newer antihypertensive agents significantly reduces the risk of major coronary events, stroke, coronary heart disease and all-cause mortality. Among the elderly population, there appears to be no age threshold beyond which treatment of hypertension, including ISH, should not be considered beneficial. Clinical management has to take into account some specific aspects related to its pathophysiology and the patient characteristics of this population. Although the therapeutic goal is < 140/90 mmHg, a decrease of 20-30 mmHg in SBP, even if the overall goal is not achieved, is associated with improved prognosis.

Bilateral Pallidal Stimulation for Cervical Dystonia

We sought to identify optimal paradigms of bilateral globus pallidus internus (GPi) stimulation in 3 subsequent patients with severe cervical dystonia. At low frequency stimulation (50–60 Hz) with wide pulse width (500 µs) and high amplitude (4.5–8.0 V), we observed immediate and consistent improvement of dystonia and dystonia-associated pain. Stimulation of the posteroventral portion of the GPi led to pronounced alleviation of dystonia; stimulation of the anterodorsal portion or at the dorsal border of the GPi resulted in significant worsening of symptoms. The therapeutic benefit obtained by using the optimal stimulation parameters continues and has lasted for at least 1 year in each patient.

Detecting randomly modulated pulses in noise

All signals that are normally called “periodic” have some amplitude and phase variation from period to period. For example an active sonar system transmits a periodic pulse train to detect targets. The received pulses are not perfectly periodic due to random modulation of the pulses from scattering and attenuation. Target scattering and propagation distortion of the transmitted and received signals produce seemingly random variation from pulse to pulse. A stochastic nonparametric model of period-to-period variation is presented in this paper. This model is used to derive an asymptotic likelihood-ratio test for wide bandwidth pulses that undergo a random modulation from pulse to pulse. It is shown that the test statistic is a linear combination of the matched filter using the expected value of the received signal as the matching vector and the signal's periodogram.

Brillouin light scattering analysis of three-magnon splitting processes in yttrium iron garnet films

Wave vector and frequency selective Brillouin light scattering (BLS) has been used to measure the wave vector make up for the dipole exchange spin wave (DESW) modes which are parametrically excited by propagating magnetostatic surface wave (MSSW) pulse signals in a long and narrow yttrium iron garnet film strip through three magnon splitting processes. The signal frequency ${f}_{s}$ was 2.65 GHz, the input pulse width was 100 ns, and the in-plane applied field was 340 Oe. In addition, time and space resolved (TSR) BLS techniques were used to map the spatio-temporal propagation properties of the MSSW and DESW modes as they evolve as a result of three magnon processes. The film thicknesses were 5--10 \ensuremath{\mu}m. Specific data are reported for an 8.7 \ensuremath{\mu}m thick film. The DESW mode frequencies are at about ${f}_{s}/2.$ The DESW wave vector k directions form lobes at in-plane angles of 5\ifmmode^\circ\else\textdegree\fi{}--15\ifmmode^\circ\else\textdegree\fi{} relative to the field. The k values are in the ${10}^{4}\mathrm{r}\mathrm{a}\mathrm{d}/\mathrm{c}\mathrm{m}$ range and are quantized. The frequencies and k values match those predicted from the dispersion relations and energy and momentum conservation. Specific critical powers are associated with particular k values. The TSR data show that the MSSW pulses propagate with a wedge shaped wave front and quench in such a way as to produce the ultra short 1--2 ns wide output pulses reported previously. The quench is connected with the appearance of a corresponding half frequency DESW wedge which is nearly stationary, has a response time of a few nanoseconds, and has a decay time in excess of the 100 ns MSSW pulse width.

Study of critical behavior in concrete during curing by application of dynamic linear and nonlinear means.

The monitoring of both linear and nonlinear elastic properties of a high performance concrete during curing is presented by application of compressional and shear waves. To follow the linear elastic behavior, both compressional and shear waves are used in wide band pulse echo mode. Through the value of the complex reflection coefficient between the cell material (Lucite) and the concrete within the cell, the elastic moduli are calculated. Simultaneously, the transmission of a continuous compressional sine wave at progressively increasing drive levels permits us to calculate the nonlinear properties by extracting the harmonics amplitudes of the signal. Information regarding the chemical evolution of the concrete based upon the reaction of hydration of cement is obtained by monitoring the temperature inside the sample. These different types of measurements are linked together to interpret the critical behavior.

Blood pressure and long-term mortality in United States hemodialysis patients: USRDS Waves 3 and 4 Study

The long-term prognostic associations of pre- and post-dialysis blood pressures, interdialytic weight gain, and antihypertensive use in hemodialysis patients are unclear. The United States Renal Data System (USRDS) Dialysis Morbidity and Mortality Waves 3 and 4 Study, a randomly generated sample of 11,142 subjects receiving hemodialysis on December 31, 1993, was examined, with vital status followed until May 2000. Pre- and post-dialysis blood pressure values, interdialytic weight gain and number of antihypertensives averaged 151.8/79.7, 137.0/74, 3.6% and 0.76, respectively. Prognostic discrimination was maximized by considering pre- and post-systolic and diastolic blood pressure values simultaneously, in a pattern suggesting that wide pulse pressures were associated with mortality (P < 0.0001). Comorbidity adjustment markedly affected associations, with low pre-dialysis diastolic (P < 0.05), low post-dialysis dialysis diastolic pressure (P < 0.05), high post-dialysis dialysis systolic pressure (P < 0.05), and high interdialytic weight gains (P = 0.005) associated with mortality. Each class of antihypertensive drug, except angiotensin-converting enzyme (ACE)-inhibitors, was associated with lower mortality in unadjusted models, an effect most pronounced for beta-blockers (hazards ratio 0.72, 95% CI 0.66 to 0.79, P < 0.0001). Comorbidity adjustment eliminated survival associations for each antihypertensive class except beta-blockers. Pre- and post-dialysis blood pressure values have independent associations with mortality, in a way that implicates wide pulse pressures. Much of the adverse prognosis of wide pulse pressures probably reflects older age and cardiovascular comorbidity. Large interdialytic weight gains are associated with shorter survival when comorbidity is taken into account. Beta-blocker use shows a robust association with survival, and may be protective.

Risk evaluation and therapeutical implications of pulse pressure in primary arterial hypertension.

Analysis of the results raised in the Framingham and the MRFIT study have clearly shown that increased pulse pressure is an independent cardiovascular risk factor. This is valid for all age groups and both sexes. The risk increases with pulse pressures over 60 - 65 mmHg for office blood pressure and 53 mmHg for 24-h-mean of ambulatory blood pressure. Pulse pressure is strongly correlated with systolic blood pressure and will be highest in case of isolated systolic hypertension. Urinary albumin excretion and left ventricular hypertrophy are closely associated with pulse pressure. With elevated pulse pressure cardiovascular risk is increased 2- to 4-fold in relation to age and endpoint. The risk of myocardial infarction is raised more if pulse pressure is associated with low mean arterial blood pressure while risk of stroke is increased with wide pulse pressure and high mean arterial pressure. The risk of pulse pressure can be seen in normotensives and in early pregnancy. Therapeutic management of pulse pressure will be similar to that of systolic blood pressure, since normalization of systolic blood pressure will also lower or normalize pulse pressure. Results of preliminary studies suggest that diuretics are superior to other drugs in decreasing pulse pressure. An increase of pulse pressure during therapy should be avoided since each 10 mmHg increase in pulse pressure will raise the risk of stroke and myocardial infarction about 24 % and 32 %.

Two-frequency mutual coherence function of electromagnetic waves in random media: a path-integral variational solution.

By use of path-integral methods, a general expression is obtained for the two-frequency, two-position mutual coherence function of an electromagnetic pulse propagating through turbulent atmosphere. This expression is valid for arbitrary models of refractive-index fluctuations, wide band pulses, and turbulence of arbitrary strength. The approach presented in this paper was examined in the cases of plane-wave, spherical wave, and Gaussian beam propagation in power-law turbulence and compared with existing numerical and exact results. A number of new results were obtained for the Gaussian beam pulse. Expressions derived here should be applicable to a wide range of practical pulse propagation problems.

Excitation Dynamics in Eukaryotic PS I from Chlamydomonas reinhardtii CC 2696 at 10 K. Direct Detection of the Reaction Center Exciton States

Excitation energy transfer in PS I particles from the green alga Chlamydomonas reinhardtiiCC 2696 was studied at 10 K by femtosecond transient absorption spectroscopy. Five-nm wide excitation pulses at 670, 680, 695, and 700 nm were applied to selectively excite different spectral forms contributing to the wide Q Y transition band of chlorophyll a. Absorbance changes between 630 and 770 nm, up to 100 ps after excitation, were collected with a time step of 54 fs during the first 5 ps. Excitation at 700 nm leads to a structured initial absorbance difference spectra with four positive bands clearly resolved at 634, 645, 652, and 661 nm, and four negative bands at 667, 675, 684, and 695 nm. These spectra are interpreted in terms of excitonic coupling between the six electron-transfer chlorophyll a molecules: a special pair, two accessory and two A0 chlorophylls. The negative bands were ascribed to photobleaching of the four one-exciton states in line with theoretical predictions (Beddard, G. S. J. Phys. Chem. B. 1998, 102, 10 966), and the positive ones to excited-state absorption. The significance of the broad absorbance changes is proposed to be the introduction of spectral overlap between the reaction center and different spectral forms of the antenna chlorophylls that is expected to increase the efficiency of energy flow to the reaction center. Excitation at different wavelengths shows indeed that trapping can occur from different spectral pools of chlorophylls with similar efficiency (trapping time 29-44 ps). Following the excitation at 670 and 680 nm, trapping was shown to occur from the same pool as at room temperature centered at 682-685 nm, containing apparently only a minority of antenna molecules located close to the reaction center. The trapping time was found to be only slightly longer compared to that at room temperature (20-23 ps at RT). At 10 K, a significant amount of chlorophylls cannot exchange excitation energy with their neighbors. Our results are consistent with previous reports that at cryogenic temperatures, charge separation is possible in 50% of PS I particles and that excitation quenching by the oxidized and reduced primary donor is equally effective. As was observed at room temperature, there is no indication of red chlorophylls absorbing above 700 nm. This lack of red chlorophylls makes it possible to directly excite reaction center chlorophylls and study interaction between them in wild type and, in future, mutant PS I from Chlamydomonas.

J-shaped relationship between blood pressure and mortality in hypertensive patients: new insights from a meta-analysis of individual-patient data.

Population-based longitudinal studies of hypertension have usually shown a continuous and positive relationship between blood pressure and mortality. However, several studies in hypertensive patients receiving treatment have described this relationship as J-shaped, with an increased risk for events in patients with low blood pressure. To assess the evidence for a J-shaped relationship between blood pressure and mortality and its relation to treatment. Meta-analysis of individual-patient data. Seven randomized clinical trials from the INDANA (INdividual Data ANalysis of Antihypertensive intervention) database. 40 233 persons with hypertension (mean follow-up, 3.9 years). Primarily beta-blockers or thiazide diuretics versus placebo or no treatment. Diastolic and systolic blood pressure and number of cardiovascular, noncardiovascular, and all-cause deaths in yearly periods of follow-up. The analysis included data on 1655 deaths (56% cardiovascular). A J-shaped relationship between diastolic blood pressure and risk for death was observed for total and cardiovascular mortality in treated patients (nadir, 84 and 80 mm Hg, respectively) and untreated patients (nadir, 90 and 85 mm Hg, respectively). For noncardiovascular deaths, the relationship was J-shaped in the treated group (nadir, 84 mm Hg) and negative in the control group. Similar results were observed for systolic blood pressure. The presence of patients with wide pulse pressure did not explain these findings. The increased risk for events observed in patients with low blood pressure was not related to antihypertensive treatment and was not specific to blood pressure-related events. Poor health conditions leading to low blood pressure and an increased risk for death probably explain the J-shaped curve.

Characterization of InAlAs/InGaAs/InP mid-infrared quantum cascade lasers

A mid-infrared laser characterization system, including a gpib programmable I– P and I– V set-up based on direct waveform measurement with extraordinary wide pulse duration and duty cycle tuning range, in conjunction with a Fourier transform infrared spectroscopy system adapted with double modulation technique, has been developed. Based on this characterization system, the characteristics of gas source MBE grown InAlAs/InGaAs/InP quantum cascade lasers (QCL), especially their thermal property, have been evaluated. The results show that in the combination of I– P, I– V and spectral measurements at various driving pulse parameters, the thermal resistance, lasing conditions as well as spectral characteristics of the mid-infrared QCL could be deduced. This characterization system is also a useful tool for the evaluation of other types of diode lasers in the mid-infrared band.

Implications of the Lag‐Luminosity Relationship for Unified Gamma‐Ray Burst Paradigms

Spectral lags (tau(sub lag)) are deduced for 1437 long (T(sub 90) greater than 2 s) BATSE gamma-ray bursts (GRBs) with peak flux F(sub p) greater than 0.25 photons cm(sup -2)/s, near to the BATSE trigger threshold. The lags are modeled to approximate the observed distribution in the F(sub p)-T(sub lag) plane, realizing a noise-free representation. Assuming a two-branch lag-luminosity relationship, the lags are self-consistently corrected for cosmological effects to yield distributions in luminosity, distance, and redshift. The results have several consequences for GRB populations and for unified gamma-ray/afterglow scenarios which would account for afterglow break times and gamma-ray spectral evolution in terms of jet opening angle, viewing angle, or a profiled jet with variable Lorentz factor: A component of the burst sample is identified - those with few, wide pulses, lags of a few tenths to several seconds, and soft spectra - whose Log[N]-Log[F(sub p)] distribution approximates a -3/2 power-law, suggesting homogeneity and thus relatively nearby sources. The proportion of these long-lag bursts increases from negligible among bright BATSE bursts to approx. 50% at trigger threshold. Bursts with very long lags, approx. 1-2 less than tau(sub lag) (S) less than 10, show a tendency to concentrate near the Supergalactic Plane with a quadrupole moment of approx. -0.10 +/- 0.04. GRB 980425 (SN 1998bw) is a member of this subsample of approx. 90 bursts with estimated distances less than 100 Mpc. The frequency of the observed ultra-low luminosity bursts is approx. 1/4 that of SNe Ib/c within the same volume. If truly nearby, the core-collapse events associated with these GRBs might produce gravitational radiation detectable by LIGO-II. Such nearby bursts might also help explain flattening of the cosmic ray spectrum at ultra-high energies, as observed by AGASA.

Pathophysiology of hypertension in the elderly.

Systolic hypertension is the most common type of hypertension in the elderly and a major modifiable cardiovascular risk factor. Systolic hypertension is associated with a wide pulse pressure resulting largely from excessive large artery stiffness. Arterial stiffness increases with age independently of mean blood pressure or the presence of other risk factors. In this review, the authors discuss the effects of age and blood pressure on arterial stiffness, the physiology of arterial compliance, and the anatomic changes of large arteries with aging. In most studies reported in the literature, elderly populations are relatively small. The role of both age and gender on arterial stiffness and wave reflection has been poorly investigated, particularly in subjects over 70 years. In this elderly population, further research is needed concerning the pathophysiology, epidemiology, and pharmacology of hypertension.

Evaluation of Resting Blood Pressures, Left Ventricular Function and Mass in Young Children with Successful Coarctoplasty in Infancy

Background and Objectives:Cardiovascular morbidities and mortalities due to persistent hypertension, left ventricular (LV) dysfunction and increased LV mass have been reported in adolescents and adults with successful coarctoplasty. We evaluated progressive properties by measuring resting blood pressures (BP), LV functions and the masses in young children with successful coarctoplasty in infancy. Subjects and Methods: BP in the right arm and the left ankle, LV function and mass, by the use of M-mode and pulsed wave Doppler ultrasound, were measured in 25 patients, with a mean age of 6.4±3 years;and a mean age at the time of repair of 0.22±0.24 years, and in 22 control subjects, with a mean age of 5.8±2.4 years. All subjects were divided into two groups based on age (more than 5 years of age and less than 5 years of age) and were analyzed independently. Results:BP in the right arm and left ankle, LV function and mass showed no consistent differences between the two groups. However, as age increased, there was a tendency of wide pulse pressure (PP) in the right arm of patients contrary to that in the control subjects. The relative increase in the PP was mainly due to a relative decrease in the diastolic BP. There was a significant increase in the LV mass index of patients with increasing age (p<0.01). The LV mass index showed significant positive correlations with the systolic BP (p<0.05) and the pulse pressure (p<0.05) of the right arm of the patients. Conclusion:We recommend careful long-term follow-up through out adulthood to reduce morbidity and mortality, even for children who received successful coarctoplasty in early infancy. (Korean Circulation J 2002;32 (9):829-836)

OTDM transmitter using WDM-TDM conversion with an electroabsorption wavelength converter

An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal.

Design of Back-bombardment-less Thermionic RF Gun

A new type of compact, back-bombardment-less RF gun is proposed. The new S-band RF gun will be useful for wide pulse operation. The performance of this RF gun is evaluated by using the 3D electromagnetic simulation code; MW-Studio and the beam tracking code; GPT. The simulation results for the new RF gun with the conventional one are presented.

Sustained contractions produced by plateau-like behaviour in human motoneurones.

Electrical stimulation over human muscle can generate force directly by activation of motor axons and indirectly by 'reflex' recruitment of spinal motoneurones. These experiments were designed to define the properties of the centrally generated 'reflex' force, including the optimal stimulus conditions for producing it in tibialis anterior (TA) and triceps surae (TS), and its interaction with volition. Subjects (n = 21) were seated with their foot strapped to an isometric myograph. Surface EMG was recorded from TS and TA. High-frequency electrical stimulation (100 Hz) of TS and TA with wide pulse widths (1 ms) was most effective to evoke the sustained centrally generated forces. The maximal force evoked by this mechanism during stimulation of TA for 40 s was approximately 42 % of that produced by a maximal voluntary contraction. For both muscle groups, ramp increases and decreases in stimulus frequency (from approximately 4 to 100 Hz and back to 4 Hz over 6 s) resulted in marked hysteresis in the force-frequency plot. After a single 'burst' of 100 Hz stimulation during prolonged stimulation at 25 Hz, force remained elevated. Repeated bursts often generated progressively larger force increments. These behaviours were abolished by an anaesthetic nerve block proximal to the stimulation site, confirming the central origin for the 'extra' force. After a brief voluntary contraction was performed during 25 Hz stimulation, force remained elevated, and this showed some gradation with voluntary contraction amplitude. Sometimes voluntary contractions alone initiated the sustained central motor output. Involuntary contractions often persisted for many seconds after electrical stimulation ceased. These were not terminated by brief inhibitory inputs to the active motoneurones but could be stopped by the voluntary command to 'relax completely'. Overall, these centrally generated contractions are consistent with activation of plateau potentials in motoneurones innervating the ankle dorsiflexors and plantarflexors. Large forces can be produced through this mechanism. The interaction with volitional drives suggests that plateau behaviour may contribute significantly to the normal output of human motoneurones.