Range Of Pulse Rates Research Articles

Passive acoustic monitoring of nocturnal fish sounds in Quintana Roo, Mexico

The Mesoamerican Reef (MAR) system has major ecological and economic importance, yet faces threats to ecosystem health and is understudied. Current methods for monitoring marine life in the northern MAR system off the state of Quintana Roo, Mexico, are inadequate for assessing the nocturnal biology and ecology of fishes, including quantification of abundance and diversity. In the present study, a marine passive acoustic monitoring (MPAM) approach was initiated at a site within the MAR system to characterize localized temporal patterns in fish acoustic behavior. This is the first study to collect data on fish sound production at night in this region. Pulsed fish sounds were a major contributor to the nighttime soundscape and were persistent and low frequency (50–1000 Hz), with a wide range of pulse rates. Fish sounds were more frequent, more persistent, and more diverse at night than during the day. Nocturnally-active fish are a more important part of the local ecosystem than had previously been recognized. Implementation of MPAM in this area has great potential as a long-term fish monitoring technique.

A fast, stochastic, and adaptive model of auditory nerve responses to cochlear implant stimulation

Cochlear implants (CIs) rehabilitate hearing impairment through direct electrical stimulation of the auditory nerve. New stimulation strategies can be evaluated using computational models. In this study, a computationally efficient model that accurately predicts auditory nerve responses to CI pulse train input was developed. A three-dimensional volume conduction and active nerve model developed at Leiden University Medical Center was extended with stochasticity, adaptation, and accommodation. This complete model includes spatial and temporal characteristics of both the cochlea and the auditory nerve. The model was validated by comparison with experimentally measured single fiber action potential responses to pulse trains published in the literature. The effects of pulse rate and pulse amplitude on spiking patterns were investigated. The modeled neural responses to CI stimulation were very similar to the single fiber action potential measurements in animal experiments. The model's responses to pulse train stimulation with respect to spatial location were also investigated. Adaptation was stronger at the borders of the stimulated area than in the center. By combining spatial details with long-term temporal components and a broad implementation of stochasticity a comprehensive model was developed that was validated for long duration electric stimulation of a wide range of pulse rates and amplitudes. The model can be used to evaluate auditory nerve responses to cochlear implant sound coding strategies.

Variations in Carrier Pulse Rate and the Perception of Amplitude Modulation in Cochlear Implant Users

A major focus of recent attempts to enhance cochlear implant (CI) systems has been to increase the rate at which pulses are delivered to the electrode array. One basis for these attempts has been the expectation that faster stimulation rates would lead to an enhanced representation of temporal modulation information. However, there is recent physiological and behavioral evidence to suggest that the reverse may be the case. Here, the effects of stimulation rate on the perception of amplitude modulation were assessed using both modulation detection and modulation frequency discrimination tasks for a range of pulse rates extending considerably higher than the highest rate tested in previous studies and for different speech-relevant modulation frequencies. Detection of sinusoidal amplitude modulation was assessed in five CI users using monopolar pulse trains presented to a single electrode at rates of 482, 723, 1447, 2894, and 5787 pulses per second (pps). Adaptive procedures were used to find the minimal detectable modulation depth at modulation frequencies of 10 and 100 Hz and at carrier levels of 25%, 50%, and 75% of the electrode's dynamic range. Discrimination of modulation frequency was examined for the same range of pulse rates for the highest carrier level. Similar adaptive procedures determined the minimum increase in modulation frequency that could be detected relative to reference modulation frequencies of 10, 100, and 200 Hz. In both tasks, level roving was implemented to minimize possible loudness cues. Consistent with previous evidence, modulation detection thresholds were better for higher carrier levels and lower modulation frequencies. When modulation depth at threshold was expressed in terms of the ratio of the depth of the modulation and the carrier level in dB (i.e., 20 log m), performance was significantly better at lower pulse rates. However, when modulation depth was expressed relative to dynamic range, the effect of pulse rate was no longer significant, reflecting the fact that dynamic range increases with pulse rate. Modulation frequency discrimination clearly worsened with increasing modulation frequency, but there was no significant effect of pulse rate. In contrast to some recent evidence, no clearly harmful effect of higher pulse rates on modulation perception was found. However, even with very fast stimulation rates, tested over a wide range of modulation frequencies and with two different tasks, there is no evidence of benefit from faster stimulation rates in the perception of amplitude modulation.

Dynamics of glutamatergic synapses in the medial vestibular nucleus of the mouse

During sinusoidal rotation or translation, primary vestibular afferents modulate their discharge rates at the frequency of motion, effectively transmitting frequency-modulated (FM) signals. This study indicates a possible role for excitatory synapses in the processing of FM signals by vestibular brainstem pathways. Inputs to medial vestibular neurons were activated with FM pulse trains, while inhibitory transmission was blocked. The relationship between the presynaptic pulse rate and the postsynaptic membrane potential was found to be linear within a range of pulse rates. Short-term plasticity was a factor contributing to sensitivity at higher modulating frequencies. The amount of low-pass filtering was correlated with excitatory postsynaptic potential (EPSP) shape, which affected temporal summation during the train. Although the NMDA component of glutamatergic transmission affected EPSP shape, it made only a minor contribution to the dynamics of synaptic transmission. Most responses showed low-pass filtering over the entire 1-16 Hz range. Overall, excitatory synapses in the medial vestibular nucleus contribute a low-pass filter to central vestibular processing and complement the high-pass filtering that is introduced both by peripheral vestibular dynamics and by the intrinsic dynamics of secondary vestibular neurons.

Alternative pulse shapes in electrical hearing

Cochlear implants (CIs) stimulate the auditory nerve with trains of symmetric biphasic (BI) pulses. We review studies showing that more efficient stimulation can be achieved by modifying these pulses by (1) increasing the inter-phase gap (IPG) between the two phases of each pulse, thereby delaying the recovery of charge, (2) increasing the duration and decreasing the amplitude of one phase - so-called "pseudomonophasic (PS)" waveforms, and (3) combining the pseudomonophasic stimulus with an IPG in a "delayed pseudomonophasic" waveform (PS_IPG). These efficiency gains, measured using changes in threshold and loudness, occur at a wide range of pulse rates, including those commonly used in current CI systems. In monopolar mode, dynamic ranges are larger for PS and for long-IPG pulse shapes than for BI pulses, but this increase in DR is not accompanied by a higher number of discriminable loudness steps, and hence, in a better coding of loudness. Moreover, waveforms with relatively short and long interphase gaps do not yield different patterns of excitation despite the relatively large differences in threshold. Two important findings are that, contrary to data obtained in animal experiments, anodic currents are more effective than cathodic stimulation for human CI patients and that the thresholds decrease with increases in IPG over a much longer time course (more than 3 ms) than for animals. In this review it is discussed how these alternative pulse shapes may be beneficial in terms of reducing power consumption and channel interactions, which issues remain to be addressed, and how models contribute to guiding our research.

Developmental plasticity of mating calls enables acoustic communication in diverse environments

Male calls of the katydid Neoconocephalus triops exhibit substantial developmental plasticity in two parameters: (i) calls of winter males are continuous and lack the verse structure of summer calls and (ii) at equal temperatures, summer males produce calls with a substantially higher pulse rate than winter males. We raised female N. triops under conditions that reliably induced either summer or winter phenotype and tested their preferences for the call parameters that differ between summer and winter males. Neither generation was selective for the presence of verses, but females had strong preferences for pulse rates: only a narrow range of pulse rates was attractive. The attractive ranges did not differ between summer and winter females. Both male pulse rate and female preference for pulse rate changed with ambient temperature, but female preference changed more than the male calls. As a result, the summer call was attractive only at 25 degrees C, whereas the slower winter call was attractive only at 20 degrees C. Thus, developmental plasticity of male calls compensates for differences in temperature dependency between calls and preferences and enables the communication system to function in heterogeneous environments. The potential role of call plasticity during the invasion of new habitats is discussed.

How much tachycardia in infants can be attributed to fever?

Study objectives We evaluate the hypothesis that pulse rate increases linearly with increased body temperature in infants and determine how much tachycardia in infants can be explained by a 1°C (1.8°F) increase in body temperature. Methods Infants younger than 1 year and presenting to a pediatric emergency department were prospectively enrolled. Rectal temperature and pulse rate were measured. Research personnel rated behavioral state as sleeping, awake and quiet, fussy, or crying. Patients were excluded if they were fussy or crying or if they had any medical condition expected to cause tachycardia. The remaining patients were divided into 6 age-based groups. Linear regression analysis of pulse rate and temperature was performed for each group. Results Four hundred ninety patients were enrolled. Pulse rate increased linearly with temperature in all age groups older than 2 months (adjusted r 2=0.102 to 0.376) but not in infants younger than 2 months (adjusted r 2=0.004). In infants aged 2 months or older, a multivariate linear regression model adjusted for age showed that pulse rate increased an average of 9.6 beats/min (95% confidence interval 7.7 to 11.5) per 1°C (1.8°F) increase in temperature (adjusted r 2=0.225). At any given temperature, the prediction interval for an individual's pulse rate had a span of approximately 64 beats/min. Conclusion In infants 2 to 12 months of age, pulse rate increases linearly with body temperature, with a mean increase of 9.6 beats/min for each 1°C (1.8°F) increase in body temperature. Pulse rates of individual infants vary greatly, however, with a broad range of pulse rates observed at any given temperature.

Investigation of a pulsed magnetron sputtering discharge with a vacuum pentode modulator power supply

A pulsed magnetron sputtering discharge at different modes of discharge ignition and a large range of duty cycles and pulse rates from single pulses to 50 kHz was investigated. A 2 kV vacuum pentode modulator was used for the generation of current pulses with amplitudes up to 2 A and target power densities up to 145 W/ cm 2 . Ignition of a pulsed discharge occurs with some delay, but still at the rise of the voltage pulse, if in the inter-electrode gap either a starting-up discharge with a current of some tens of milliamperes is sustained or if the residual concentration of charged particles after a previous pulse is still high enough. A spike of electron current to the substrate with energies up to 100 eV is generated at the current front of the high-current discharge when the voltage drops to its equilibrium value. These electrons are presumably secondary electrons. The effective cathode secondary emission and gas ionization take place at the current front when the voltage drop at the gap is higher than the equilibrium value. Therefore, the duration of the current front lasts only some microseconds and an excess concentration of charged particles is generated in the gap. During the high-current discharge stage the plasma expands with the velocity of ambipolar diffusion from the near-target region. The ion current to substrate reaches its maximum value after some tens of microseconds. For this reason, the pulse duration should not be lower than 20– 40 μs for ion-assisted deposition. In the afterglow period deionization of the post-discharge plasma takes place. Due to the surplus ion conductivity of the plasma the starting-up discharge is suppressed. With delay in self-restoring the starting-up discharge is some tens of microseconds. This time determines the duration of maximum pauses between the control pulses without the starting-up discharge. Thus, work in the middle-frequency range of pulse rates allows to exclude a starting-up discharge and to obtain the lowest delay for establishing the magnetron discharge at each of the following pulses.

Pulsed supersonic molecular beam growth of AlN

Non-skimmed pulsed supersonic free jets of trimethylaluminum (TMA) and ammonia are used to grow thin films of AlN. The translational kinetic energy of the precursors used for growth trials is 130 meV for TMA and 160 and 500 meV for ammonia. Effects of varying each pulse rate, substrate temperature, and deposition time on film composition and growth rate are studied. The resulting films were nearly always oriented with the non-polar (10⋅0) plane parallel to the silicon substrate (001) plane or to the sapphire substrate basal plane. The measured lattice parameter ratio c/a is 1.594. Film growth only occurred in a narrow range of pulse rates. Films can be grown over the temperature range of 900–1200 K. An average growth rate of 0.115 μm/h is measured. AlN films could also be grown when the substrates were not directly in the beam path. The role of precursor flux on film growth is discussed. Additional post-deposition analysis includes Fourier transform infrared spectroscopy, reflectance spectroscopy, scanning electron microscopy, and Auger electron spectroscopy.

Lack of a tachycardic response to hypotension in penetrating abdominal injuries

Vital signs upon arrival to the emergency department were studied retrospectively in 59 consecutive patients with isolated penetrating abdominal injuries to determine their chronotropic response to hypotension. Forty-three patients with documented intraperitoneal injury were included in the study and separated into hypotensive and normotensive groups using a systolic blood pressure of 90 or 100 mm Hg. The difference in mean pulse rates between normotensive and hypotensive groups was not statistically significant ( P>0.05) although a wide range of pulse rates was noted in both groups. Nearly half of all hypotensive patients were not tachycardic, defined as a pulse rate < 100. Similar findings were observed when the 117 sets of vital signs recorded both in the field and in the emergency department were analyzed as independent pieces of data. Several mechanisms are proposed for the lack of tachycardia in the presence of hypotension. This data suggest that tachycardia may not be a reliable sign of hypovolemic shock when defined by blood pressure criteria in these patients.

A method to reduce deflection aberrations in electron-beam lithography systems.: W Knauer, J Vac Sci Technol, 19 (4), 1981, 1042–1047

A pulsed magnetron sputtering discharge at different modes of discharge ignition and a large range of duty cycles and pulse rates from single pulses to 50kHz was investigated. A 2kV vacuum pentode modulator was used for the generation of current pulses with amplitudes up to 2A and target power densities up to 145W/cm2.Ignition of a pulsed discharge occurs with some delay, but still at the rise of the voltage pulse, if in the inter-electrode gap either a starting-up discharge with a current of some tens of milliamperes is sustained or if the residual concentration of charged particles after a previous pulse is still high enough. A spike of electron current to the substrate with energies up to 100eV is generated at the current front of the high-current discharge when the voltage drops to its equilibrium value. These electrons are presumably secondary electrons. The effective cathode secondary emission and gas ionization take place at the current front when the voltage drop at the gap is higher than the equilibrium value. Therefore, the duration of the current front lasts only some microseconds and an excess concentration of charged particles is generated in the gap.During the high-current discharge stage the plasma expands with the velocity of ambipolar diffusion from the near-target region. The ion current to substrate reaches its maximum value after some tens of microseconds. For this reason, the pulse duration should not be lower than 20–40μs for ion-assisted deposition.In the afterglow period deionization of the post-discharge plasma takes place. Due to the surplus ion conductivity of the plasma the starting-up discharge is suppressed. With delay in self-restoring the starting-up discharge is some tens of microseconds. This time determines the duration of maximum pauses between the control pulses without the starting-up discharge. Thus, work in the middle-frequency range of pulse rates allows to exclude a starting-up discharge and to obtain the lowest delay for establishing the magnetron discharge at each of the following pulses.

EVOLUTIONARY ASPECTS OF MATING CALL VARIATION IN A DIPLOID-TETRAPLOID SPECIES COMPLEX OF TREEFROGS (ANURA).

Sound spectrographic analysis demonstrated that the two mating call types of the nominal species Hyla versicolor (fastpulsed and slow-pulsed) are distributed in a definite geographic pattern in the eastern half of the United States (Blair, 1958a). Crosses between the call types, and backcrosses of F1 progeny to the parental types, exhibit a high degree of mortality compared with within call type crosses, whether from sympatric populations, from populations in near allopatry, or from widely allopatric populations (Johnson, 1959, 1963; Ralin, 1976a). Females choose their own call type in discrimination tests (Littlejohn et al., 1960). There are statistically significant but overlapping differences between the two call types in some mensural characters (Johnson, 1961, 1966; Ralin, 1968). The name H. versicolor now represents the slow-call species, the subspecific name chrysoscelis has been elevated to species rank to represent the fast-call species, and the three formerly described subspecies are considered to be invalid (Johnson, 1966). Sound spectrograms and oscilloscope tracings of the mating calls of the two species were presented by Pierce and Ralin (1972). When uncorrected for temperature, the range of pulse rates in H. versicolor (17-35 pulses/s) and H. chrysoscelis (34-69 pulses/s) overlap slightly (Johnson, 1966). However, when corrected for the effects of temperature, there is no overlap in central Texas (Ralin, 1968) or Del-Mar-Va peninsula and New Jersey (Zweifel, 1970) populations of the two species. Karyotypic analysis demonstrated that H. versicolor from northern New Jersey is a sexually reproducing tetraploid population with 4N = 48 chromosomes (Wasserman, 1970). Electrophoretic comparisons of polymorphic loci in populations of H. versicolor from central Texas and populations of H. chrysoscelis from central Texas and east of the Mississippi River indicated that H. versicolor is also tetraploid in Texas (reported by Ralin et al., at Austin, Texas Meeting of Soc. Study of Evolution, 1970; Ralin and Selander, 1977). In every instance of cytological examination, individuals identified by call as H. versicolor proved to be tetraploid, and individuals identified by call as H. chrysoscelis proved to be diploid (Bogart and Wasserman, 1972; Bogart, pers. comm.). Electrophoretic analysis of the Ldb (lactate dehydrogenase-B or heart LDH) locus also indicated that central Texas (western) populations of H. chrysoscelis are genetically differentiated from eastern populations (South Carolina, Georgia, Ohio, and Mississippi), and that both groups of populations apparently have contributed alleles to the formation of Texas H. versi-color (Ralin, 1976b; Ralin and Selander,, 1977). Recent evidence indicates that. males of H. chrysoscelis from near Savan-nah, Georgia have significantly lowerpulse rates and significantly longer call durations than males of H. chrysoscelis from central Texas, and that females from the Savannah area prefer the call of a male from the same population to a central Texas call (Gerhardt, 1974b). An analysis of mating call along northern and southern transects through the ranges of the two call types led to the suggestion by Blair (1958a) that there might be more than two forms involved in this complex. However, correction for the effects of temperature

Parametric efficiency limit of resonance charging of pulse-forming network in pulse generators

The equivalent circuit of pulse generators with pulse forming network (PFN) is described. It is shown that resonance charging application of the pulse forming network is effective only for a determined range of the pulse rates. This range of pulse rates is determined by parameters of the device.

An accurate logarithmic counting-rate meter covering a wide range

The paper describes an instrument whose output voltage is proportional to the logarithm of the rate at which the input pulses are received. This relationship can be made to hold, to a good approximation, over a range of pulse rates of from 1 to 105 pulses per second without range switching.The causes of inaccuracy and instability are examined, and it is shown that errors may be expected to be less than 10% of the pulse rate throughout the range of a five-decade instrument; the errors are correspondingly smaller in an instrument covering a smaller range.The paper shows how the instrument may be used in the investigation of some problems in nuclear physics.