Pulse Response Time Research Articles

Modulations of detectable pulse response time spread in shallow water resulting from a combination of sound-speed variability and bottom loss

Reciprocal transmission tomography experiments in the Florida Straits have yielded a month-long time history of reciprocal pulse responses over three ranges approximately 22 km in length and 250 m in depth. A transmitted pulse of 8.75 ms in duration is spread out approximately 150 ms. The detectable time spread, or pulse width, is observed to vary by as much as 120 ms over time scales on the order of days. In a previous paper a strong correlation was reported between the sound-speed gradient at mid-depth and the total pulse width. A plausible explanation that changes in the sound-speed profile shape was causing the ray arrivals to focus and defocus in time was set forth as a hypothesis for this study, to be examined with range-dependent ray and PE models. The models predict a different and unexpected relation. Variations in the sound-speed profile from the average profile shape to a more convex profile increase the bottom grazing angle to the early arrivals. This results in an attenuation of the early arriving portion of the pulse below ambient noise and therefore an apparent narrowing of the pulse. Likewise, changes in the sound-speed profile from the average profile shape to a linear profile, produce smaller bottom grazing angles for the fastest arrivals, less loss, and an overall wider appearing pulse.

Epidural Anesthesia Affects Pulse Oximeter Readings and Response Time

We investigated the effects of epidural anesthesia on pulse oximeter readings (Spo2) and response time because this type of anesthesia causes significant changes in microcirculation at measurement sites. Twenty patients were divided into lumbar epidural (L-EPI;n=10) and the cervical epidural (C-EPI;n=10) groups. Spo2 and skin blood flow (SBF) were measured at the finger and toe simultaneously by pulse oximeter and laser Doppler flowmeter, respectively. Data were collected before and after epidural anesthesia for 1 min and the response time was calculated by the difference between the finger and toe using the breath-holding method. Epidural anesthesia increased SBF in the blocked area and decreased it in the nonblocked area in both groups (P<0.01, respectively). In the L-EPI group, Spo2 was increased at the finger (P<0.05) and decreased at the toe (P<0.05). In the C-EPI group, Spo2 at both the finger and toe was decreased by the anesthesia. ΔSpo2 (Spo2 at the finger minus Spo2 at the toe) was increased in the L-EPI group (P<0.05) and decreased in the C-EPI group (P<0.01). The difference in the response time became larger in the C-EPI group and smaller or opposite in the L-EPI group after anesthesia. The difference in response time and SBF were significantly correlated (r=0.71;P<0.05). These results indicated that epidural anesthesia lowerd Spo2 and shortened the response time through vasodilation in the blocked area and caused the opposite reactions in the nonblocked area through compensatory vasoconstriction.

Epidural anesthesia affects pulse oximeter readings and response time.

We investigated the effects of epidural anesthesia on pulse oximeter readings (Spo2) and response time because this type of anesthesia causes significant changes in microcirculation at measurement sites. Twenty patients were divided into lumbar epidural (L-EPI;n=10) and the cervical epidural (C-EPI;n=10) groups. Spo2 and skin blood flow (SBF) were measured at the finger and toe simultaneously by pulse oximeter and laser Doppler flowmeter, respectively. Data were collected before and after epidural anesthesia for 1 min and the response time was calculated by the difference between the finger and toe using the breath-holding method. Epidural anesthesia increased SBF in the blocked area and decreased it in the nonblocked area in both groups (P<0.01, respectively). In the L-EPI group, Spo2 was increased at the finger (P<0.05) and decreased at the toe (P<0.05). In the C-EPI group, Spo2 at both the finger and toe was decreased by the anesthesia. ΔSpo2 (Spo2 at the finger minus Spo2 at the toe) was increased in the L-EPI group (P<0.05) and decreased in the C-EPI group (P<0.01). The difference in the response time became larger in the C-EPI group and smaller or opposite in the L-EPI group after anesthesia. The difference in response time and SBF were significantly correlated (r=0.71;P<0.05). These results indicated that epidural anesthesia lowerd Spo2 and shortened the response time through vasodilation in the blocked area and caused the opposite reactions in the nonblocked area through compensatory vasoconstriction.

Epidural anesthesia affects pulse oximeter readings and response time

Epidural anesthesia affects pulse oximeter readings and response time

Nonlinear optical susceptibilities of epitaxially grown polydiacetylene measured by femtosecond time-resolved spectroscopy.

Ultrafast nonlinear optical responses in polydiacetylene-3-butoxycarbonyl methylurethane prepared by epitaxial vacuum deposition on a KCl substrate are investigated by femtosecond absorption spectroscopy. Absorbance changes due to ``instantaneous'' processes which decay within the pulse duration of 100 fs, self-trapped exciton, and triplet exciton are resolved in time. The spectra of the corresponding nonlinear optical susceptibilities are obtained considering the pulse duration and response times. The ``instantaneous'' nonlinear optical response consists of several nonlinear effects, i.e., hole burning, coherent coupling between pump polarization and probe field, Raman gain, inverse Raman scattering, and induced-phase modulation.

Wideband probing of the transauroral HF channel: Solar minimum

The Naval Research Laboratory HF Channel Prober is a high‐resolution, computer‐controlled, coded‐pulse sounder designed to study the time variable behavior of the wideband HF radio channel. Multispectral time histories of the channel pulse response and the channel scattering function are tools used in the study. Pulse response delay resolution down to 1 μs and unambiguous Doppler up to ±30 Hz are possible, depending on the choice of experiment format and operating parameters. Measurements were made quarterly between October 1985 and July 1986 on a 2300‐km transauroral path between a transmitter site at Frobisher Bay, Canadian Northwest Territories, and a receiver site near Rome, New York. Data are presented in the form of ionograms, pulse response time histories (power and coherent video), and channel scattering functions. Data for mid‐latitude and transauroral paths are compared, and their similarities and differences are discussed. The mid‐latitude channel is multimodal but is usually characterized by a single specular return per mode. The character of transauroral channel is quite variable, depending strongly on the degree of magnetic disturbance, the location of the midpath reflection point relative to the position of the auroral oval, and the mode. During quiet magnetic conditions, and with the path midpoint well below the auroral oval, channel behavior is shown to resemble a mid‐latitude channel at certain times and a specular multipath channel at other times (i.e., one where each mode comprises several distinct multipath components). Doppler spread in these cases tends to be small. At night, when the midpath point lies within the auroral oval, the return signal is diffuse, and the Doppler spread appears to be larger by an order of magnitude.

Some aspects of position‐sensitive photodetectors made of amorphous silicon

AbstractPosition‐sensitive photodetectors detect an illuminated position without using image scanning. A large area detector of dual‐axis tetralateral PSD has been fabricated using amorphous silicon for low cost. The effective area of the device was 9.6 × 9.6 mm2, the detection deviation within 2 mm from the center was 0.3 mm and the pulse response time was around 1.5 ms. The resistive divider layer using Pd and Mo thin films provided good results. The position‐sensitive characteristics were simulated numerically by using Lucovsky's equation and the result was in good agreement with the experimental result. The analytical results lead us to the conclusion that in case of two‐dimensional dual‐axis tetralateral PSD, the nonlinearity in the position coordinate of the measured signal is caused by the introduction of both coordinate components for illuminated position (x0, y0) to each signal potential components at the x or y axis.

High‐resolution probing of the HF ionospheric skywave channel: F2 layer results

A computer‐controlled, coded‐pulse, step frequency, oblique sounder has been designed to probe the HF radio communication channel to a bandwidth of 1 MHz. The instrument monitors the complex pulse response of the channel over an extended period of time thus permitting simultaneous observation of the time and frequency behavior of the channel. A coherent time history presentation of the wide band data permits unequivocal identification of individual modes in situations involving several partially overlapping modes. Channel instantaneous bandwidth and mode Doppler shift can be estimated by inspection of the pulse response time history curves. Data presentation in the wide band time history format is also very informative in the description of signal fluctuation phenomena and in understanding their underlying causes. Measurements have been made over a short‐baseline (126 km), mid‐latitude path between an island off the southern California coast and the mainland. The response of the one‐hop F2 layer sky wave mode to a 1‐μs probing pulse is used to illustrate the unique capabilities of this instrument and the unusual effects that are observed with a high‐resolution probing pulse.

High-speed ultraviolet and x-ray-sensitive InP photoconductive detectors

The performance of iron-doped InP photoconductive detectors in the optical and x-ray spectral regions is compared. The detectors show uniform, high cw quantum efficiency from 900 to 200 nm. Pulse response times at 193 nm are laser source limited to ⩽12 ns. The response to ∼9-keV-fast x-ray pulses indicates device rise times &amp;lt;90 ps.

Acoustical design of the multi-purpose ‘Hjertnes’ hall in Sandefjord

‘Hjertnes’ is a typical multi-purpose hall primarily intended for concerts. A three-dimensional ray tracing computer program was used to provide a picture of the sound energy distribution on the audience area of the hall, various room shapes being investigated. This resulted in tilted side walls and a convex ceiling. Variable acoustics have been obtained through the use of movable ceiling absorbing and diffusing elements. In addition, a demountable orchestra enclosure has been constructed within the stagehouse. Control measurements of pulse response and reverberation time are reported.

Dynamic simulation of gas chromatographic column

The dynamic behavior of a gas—liquid chromatographic column was investigated to develop methods for estimation of the pulse response and dead time. A mathematical model describing the column behavior was proposed and the resulting response curves compared with the experimental column behavior. This study indicated that the models based on assumptions of perfect mixing and plug flow could be used to predict the dead time which could represent the residence time of the solute gas through the column if enough subdivisions were used for the simulation. Van Deemter's model was verified experimentally and adequately describes the gas—liquid chromatographic column in process control computer simulation of the system. The values of the system parameters characterizing the dynamic behavior were obtained from the simulation. The pulse response curve simulation is unique for the estimation of dead time just as is the transient response curve for the steady-state time.

High Stability ``Boxcar'' Integrator for Fast NMR Transients in Solids

An improved double channel electronic sampling integrator with digital output is described which is particularly suitable for enhancing signal-to-noise in pulsed NMR studies in solids where narrow sampling gate widths and long data memory are essential. The sampling gate widths are 1 μsec or less. The difference signal between the channel inputs is converted to digital form and stored in a standard counter which may be modified to add successive counts, thereby computing the mean numerically. Since there is no analog integration the system has a pulse response time of 1 μsec. The system is free of ion or grid current drift problems common to previous designs. Thermal drift is small. Details of the circuits and graphs of integrating performance are presented.