Journal articles: 'Sweep frequency'

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Fuzessery, Z. M. "Response selectivity for multiple dimensions of frequency sweeps in the pallid bat inferior colliculus." Journal of Neurophysiology 72, no. 3 (September 1, 1994): 1061–79. http://dx.doi.org/10.1152/jn.1994.72.3.1061.

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1. While hunting, the pallid bat uses passive sound localization at low frequencies to find terrestrial prey, and echolocation for general orientation. It must therefore process two different types of acoustic input at the same time. The pallid bat's echolocation pulse is a downward frequency-modulated (FM) sweep from 60 to 30 kHz. This study examined the response selectivity of single neurons in the pallid bat's central nucleus of the inferior colliculus (ICC) for FM sweeps, comparing the response properties of the high-frequency population, tuned to the biosonar pulse, with the low-frequency population, tuned below the pulse. The working hypothesis was that the high-frequency population would exhibit a response selectivity for downward FM sweeps that was not present in the low-frequency population. 2. Neurons were tested for their selectivity for FM sweep direction, duration, frequency range and bandwidth, and rate of frequency change. The extent to which they responded exclusively to tones, noise, and FM sweeps was also examined. Significant differences in the response properties of neurons in the two populations were found. In the low-frequency population, all neurons responded to tones, but only 50% responded to FM sweeps. Only 23% were selective for sweep direction. In the high-frequency population, all neurons responded to FM sweeps, but 31% did not respond to tones. Over one-half of this population was selective for sweep direction, and of those that were selective, all preferred the downward sweep direction of the biosonar pulse. A large percentage (31%) responded exclusively to downward sweeps, and not to tones or upward sweeps. None of the cells in either population responded to noise, or did so only at very high relative thresholds. 3. Both populations contained neurons that were selective for short stimulus durations that approximated the duration of the biosonar pulse, although the percentage was greater in the high-frequency population (58% vs. 20%). In the high-frequency population, 31% of the neurons tested for duration responded exclusively to both the sweep direction and duration of the biosonar pulse. 4. Downward FM-selective neurons, with one exception, were generally insensitive to the rate of frequency change of the FM sweep, as well as the frequency range and bandwidth of the sweep. They responded similarly to both the full 60- to 30-kHz sweep and to 5-kHz bandwidth portions of the full sweep.(ABSTRACT TRUNCATED AT 400 WORDS)

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Fuzessery, Zoltan M., Marlin D. Richardson, and Michael S. Coburn. "Neural Mechanisms Underlying Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Inferior Colliculus of the Pallid Bat." Journal of Neurophysiology 96, no. 3 (September 2006): 1320–36. http://dx.doi.org/10.1152/jn.00021.2006.

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This study describes mechanisms that underlie neuronal selectivity for the direction and rate of frequency-modulated sweeps in the central nucleus of the inferior colliculus (ICC) of the pallid bat ( Antrozous pallidus). This ICC contains a high percentage of neurons (66%) that respond selectively to the downward sweep direction of the bat's echolocation pulse. Some (19%) are specialists that respond only to downward sweeps. Most neurons (83%) are also tuned to sweep rates. A two-tone inhibition paradigm was used to describe inhibitory mechanisms that shape selectivity for sweep direction and rate. Two different mechanisms can create similar rate tuning. The first is an early on-best frequency inhibition that shapes duration tuning, which in turn determines rate tuning. In most neurons that are not duration tuned, a delayed high-frequency inhibition creates rate tuning. These neurons respond to fast sweep rates, but are inhibited as rate slows, and delayed inhibition overlaps excitation. In these neurons, starting a downward sweep within the excitatory tuning curve eliminates rate tuning. However, if rate tuning is shaped by duration tuning, this manipulation has no effect. Selectivity for the downward sweep direction is created by an early low-frequency inhibition that prevents responses to upward sweeps. In addition to this asymmetry in arrival times of low- and high-frequency inhibitions, the bandwidth of the low-frequency sideband was broader. Bandwidth influences the arrival time of inhibition during an FM sweep because a broader sideband will be encountered sooner. These findings show that similar spectrotemporal filters can be created by different mechanisms.

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Razak, K. A. "Mechanisms underlying intensity-dependent changes in cortical selectivity for frequency-modulated sweeps." Journal of Neurophysiology 107, no. 8 (April 15, 2012): 2202–11. http://dx.doi.org/10.1152/jn.00922.2011.

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Frequency-modulated (FM) sweeps are common components of species-specific vocalizations. The intensity of FM sweeps can cover a wide range in the natural environment, but whether intensity affects neural selectivity for FM sweeps is unclear. Bats, such as the pallid bat, which use FM sweeps for echolocation, are suited to address this issue, because the intensity of echoes will vary with target distance. In this study, FM sweep rate selectivity of pallid bat auditory cortex neurons was measured using downward sweeps at different intensities. Neurons became more selective for FM sweep rates present in the bat's echolocation calls as intensity increased. Increased selectivity resulted from stronger inhibition of responses to slower sweep rates. The timing and bandwidth of inhibition generated by frequencies on the high side of the excitatory tuning curve [sideband high-frequency inhibition (HFI)] shape rate selectivity in cortical neurons in the pallid bat. To determine whether intensity-dependent changes in FM rate selectivity were due to altered inhibition, the timing and bandwidth of HFI were quantified at multiple intensities using the two-tone inhibition paradigm. HFI arrived faster relative to excitation as sound intensity increased. The bandwidth of HFI also increased with intensity. The changes in HFI predicted intensity-dependent changes in FM rate selectivity. These data suggest that neural selectivity for a sweep parameter is not static but shifts with intensity due to changes in properties of sideband inhibition.

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Tabas, Alejandro, and Katharina von Kriegstein. "Neural modelling of the encoding of fast frequency modulation." PLOS Computational Biology 17, no. 3 (March 3, 2021): e1008787. http://dx.doi.org/10.1371/journal.pcbi.1008787.

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Frequency modulation (FM) is a basic constituent of vocalisation in many animals as well as in humans. In human speech, short rising and falling FM-sweeps of around 50 ms duration, called formant transitions, characterise individual speech sounds. There are two representations of FM in the ascending auditory pathway: a spectral representation, holding the instantaneous frequency of the stimuli; and a sweep representation, consisting of neurons that respond selectively to FM direction. To-date computational models use feedforward mechanisms to explain FM encoding. However, from neuroanatomy we know that there are massive feedback projections in the auditory pathway. Here, we found that a classical FM-sweep perceptual effect, the sweep pitch shift, cannot be explained by standard feedforward processing models. We hypothesised that the sweep pitch shift is caused by a predictive feedback mechanism. To test this hypothesis, we developed a novel model of FM encoding incorporating a predictive interaction between the sweep and the spectral representation. The model was designed to encode sweeps of the duration, modulation rate, and modulation shape of formant transitions. It fully accounted for experimental data that we acquired in a perceptual experiment with human participants as well as previously published experimental results. We also designed a new class of stimuli for a second perceptual experiment to further validate the model. Combined, our results indicate that predictive interaction between the frequency encoding and direction encoding neural representations plays an important role in the neural processing of FM. In the brain, this mechanism is likely to occur at early stages of the processing hierarchy.

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Morrison, James A., Roberto Valdizón-Rodríguez, Daniel Goldreich, and Paul A. Faure. "Tuning for rate and duration of frequency-modulated sweeps in the mammalian inferior colliculus." Journal of Neurophysiology 120, no. 3 (September 1, 2018): 985–97. http://dx.doi.org/10.1152/jn.00065.2018.

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Responses of auditory duration-tuned neurons (DTNs) are selective for stimulus duration. We used single-unit extracellular recording to investigate how the inferior colliculus (IC) encodes frequency-modulated (FM) sweeps in the big brown bat. It was unclear whether the responses of so-called “FM DTNs” encode signal duration, like classic pure-tone DTNs, or the FM sweep rate. Most FM cells had spiking responses selective for downward FM sweeps. We presented cells with linear FM sweeps whose center frequency (CEF) was set to the best excitatory frequency and whose bandwidth (BW) maximized the spike count. With these baseline parameters, we stimulated cells with linear FM sweeps randomly varied in duration to measure the range of excitatory FM durations and/or sweep rates. To separate FM rate and FM duration tuning, we doubled (and halved) the BW of the baseline FM stimulus while keeping the CEF constant and then recollected each cell’s FM duration tuning curve. If the cell was tuned to FM duration, then the best duration (or range of excitatory durations) should remain constant despite changes in signal BW; however, if the cell was tuned to the FM rate, then the best duration should covary with the same FM rate at each BW. A Bayesian model comparison revealed that the majority of neurons were tuned to the FM sweep rate, although a few cells showed tuning for FM duration. We conclude that the dominant parameter for temporal tuning of FM neurons in the IC is FM sweep rate and not FM duration. NEW & NOTEWORTHY Reports of inferior colliculus neurons with response selectivity to the duration of frequency-modulated (FM) stimuli exist, yet it remains unclear whether such cells are tuned to the FM duration or the FM sweep rate. To disambiguate these hypotheses, we presented neurons with variable-duration FM signals that were systematically manipulated in bandwidth. A Bayesian model comparison revealed that most temporally selective midbrain cells were tuned to the FM sweep rate and not the FM duration.

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Atencio, Craig A., David T. Blake, Fabrizio Strata, Steven W. Cheung, Michael M. Merzenich, and Christoph E. Schreiner. "Frequency-Modulation Encoding in the Primary Auditory Cortex of the Awake Owl Monkey." Journal of Neurophysiology 98, no. 4 (October 2007): 2182–95. http://dx.doi.org/10.1152/jn.00394.2007.

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Many communication sounds, such as New World monkey twitter calls, contain frequency-modulated (FM) sweeps. To determine how this prominent vocalization element is represented in the auditory cortex we examined neural responses to logarithmic FM sweep stimuli in the primary auditory cortex (AI) of two awake owl monkeys. Using an implanted array of microelectrodes we quantitatively characterized neuronal responses to FM sweeps and to random tone-pip stimuli. Tone-pip responses were used to construct spectrotemporal receptive fields (STRFs). Classification of FM sweep responses revealed few neurons with high direction and speed selectivity. Most neurons responded to sweeps in both directions and over a broad range of sweep speeds. Characteristic frequency estimates from FM responses were highly correlated with estimates from STRFs, although spectral receptive field bandwidth was consistently underestimated by FM stimuli. Predictions of FM direction selectivity and best speed from STRFs were significantly correlated with observed FM responses, although some systematic discrepancies existed. Last, the population distributions of FM responses in the awake owl monkey were similar to, although of longer temporal duration than, those in the anesthetized squirrel monkeys.

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Okaya, David A., Eleni Karageorgi, Thomas V. McEvilly, and Peter E. Malin. "Removing vibrator‐induced correlation artifacts by filtering in frequency‐uncorrelated time space." GEOPHYSICS 57, no. 7 (July 1992): 916–26. http://dx.doi.org/10.1190/1.1443304.

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Vibrator‐to‐ground coupling can produce resonance‐induced energy that propagates with the primary sweep and produces serious artifacts in the correlated seismogram due to the frequency structure of this offending energy. For sweeps linearly increasing in frequency, the resulting artifact is observed (uncorrelated) to increase in frequency at a linear rate differing from the original sweep. Upon crosscorrelation with the pilot sweep, the artifact‐producing energy becomes distributed over an extended range of time while the normal reflected sweep is compressed, by design, into a narrow correlation wavelet. The resulting traces thus exhibit strong amplitudes that increase monotonically in dominant frequency. Display of individual uncorrelated seismograms using a Fourier frequency‐uncorrelated time (F-T) transformation reveals the relationship between the primary sweep and the induced artifact. “Surgical” filtering in this new F-T space provides for a first‐order removal of both the artifact and the energy in sweep harmonics as induced by the stong first arrivals. Two‐dimensional (2-D) spectral filtering of the modulus of the (complex) 2-D transform of the F-T data provides better rejection of the unwanted energy. Application of this trace‐by‐trace filtering process to a badly contaminated crustal-scale multichannel CDP profile in the southern San Joaquin Valley, California, reveals significant reflections from the middle and lower crust that were obscured in the unfiltered profile.

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Harris, Alexandre M., and Michael DeGiorgio. "Identifying and Classifying Shared Selective Sweeps from Multilocus Data." Genetics 215, no. 1 (March 9, 2020): 143–71. http://dx.doi.org/10.1534/genetics.120.303137.

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Positive selection causes beneficial alleles to rise to high frequency, resulting in a selective sweep of the diversity surrounding the selected sites. Accordingly, the signature of a selective sweep in an ancestral population may still remain in its descendants. Identifying signatures of selection in the ancestor that are shared among its descendants is important to contextualize the timing of a sweep, but few methods exist for this purpose. We introduce the statistic SS-H12, which can identify genomic regions under shared positive selection across populations and is based on the theory of the expected haplotype homozygosity statistic H12, which detects recent hard and soft sweeps from the presence of high-frequency haplotypes. SS-H12 is distinct from comparable statistics because it requires a minimum of only two populations, and properly identifies and differentiates between independent convergent sweeps and true ancestral sweeps, with high power and robustness to a variety of demographic models. Furthermore, we can apply SS-H12 in conjunction with the ratio of statistics we term H2Tot and H1Tot to further classify identified shared sweeps as hard or soft. Finally, we identified both previously reported and novel shared sweep candidates from human whole-genome sequences. Previously reported candidates include the well-characterized ancestral sweeps at LCT and SLC24A5 in Indo-Europeans, as well as GPHN worldwide. Novel candidates include an ancestral sweep at RGS18 in sub-Saharan Africans involved in regulating the platelet response and implicated in sudden cardiac death, and a convergent sweep at C2CD5 between European and East Asian populations that may explain their different insulin responses.

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Razak, Khaleel A., and Zoltan M. Fuzessery. "GABA Shapes Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Auditory Cortex." Journal of Neurophysiology 102, no. 3 (September 2009): 1366–78. http://dx.doi.org/10.1152/jn.00334.2009.

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In the pallid bat auditory cortex and inferior colliculus (IC), the majority of neurons tuned in the echolocation range is selective for the direction and rate of frequency-modulated (FM) sweeps used in echolocation. Such selectivity is shaped mainly by spectrotemporal asymmetries in sideband inhibition. An early-arriving, low-frequency inhibition (LFI) shapes direction selectivity. A delayed, high-frequency inhibition (HFI) shapes rate selectivity for downward sweeps. Using iontophoretic blockade of GABAa receptors, we show that cortical FM sweep selectivity is at least partially shaped locally. GABAa receptor antagonists, bicuculline or gabazine, reduced or eliminated direction and rate selectivity in ∼50% of neurons. Intracortical GABA shapes FM sweep selectivity by either creating the underlying sideband inhibition or by advancing the arrival time of inhibition relative to excitation. Given that FM sweep selectivity and asymmetries in sideband inhibition are already present in the IC, these data suggest a refinement or recreation of similar response properties at the cortical level.

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Grombacher, Denys, Raphael Dlugosch, Elliot Grunewald, Mike Müller-Petke, and Esben Auken. "Frequency cycling to alleviate unknown frequency offsets for adiabatic half-passage pulses in surface nuclear magnetic resonance." GEOPHYSICS 83, no. 5 (September 1, 2018): JM29—JM38. http://dx.doi.org/10.1190/geo2017-0701.1.

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Adiabatic half-passage (AHP) pulses show great promise for significantly enhancing the signal-to-noise ratio of the surface nuclear magnetic resonance (NMR) free-induction decay measurement. Performing an AHP requires that the frequency sweep terminates when the transmit frequency is equal to the Larmor frequency, a condition that demands accurate knowledge of the true Larmor frequency. If the frequency sweep is terminated at an incorrect frequency, i.e., with an unknown offset between the transmit and Larmor frequency at the end of the pulse, the net excitation is affected and it can differ from that predicted by modeling that assumes a 0 Hz offset at the end of the sweep. Surface NMR surveys using a traditional single-frequency pulse have previously been shown to display degraded performance in the presence of an uncertain Larmor frequency estimate; the AHP pulse is also likely susceptible to such degraded performance. To ensure that reliable results can be produced by AHP pulses in the presence of an uncertain Larmor frequency estimate, we have developed an approach that adapts the frequency-cycling scheme for use with AHP pulses. We hypothesize that data collected using two similar AHP pulses, each with the exact same frequency sweep but where one sweeps toward the Larmor frequency from higher frequencies and the other from lower frequencies, can be stacked in such a manner that the impact of an unknown frequency offset is significantly reduced. We present synthetic and field results to demonstrate that frequency-cycling AHP pulse surface NMR data can ensure reliable performance even in the presence of an uncertain Larmor frequency estimate.

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Williams, Anthony J., and Zoltan M. Fuzessery. "Facilitatory Mechanisms Shape Selectivity for the Rate and Direction of FM Sweeps in the Inferior Colliculus of the Pallid Bat." Journal of Neurophysiology 104, no. 3 (September 2010): 1456–71. http://dx.doi.org/10.1152/jn.00598.2009.

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The inferior colliculus (IC) of the pallid bat has a large percentage of neurons that respond selectively to the rate and direction of the bat's echolocation pulse, a downward FM sweep. Three underlying mechanisms have been previously described. Here we describe a fourth mechanism, facilitation, that shapes selectivity for both sweep rate and direction. The neurons studied are termed FM specialists, because they do not respond to tones. Most were selective for the downward sweep direction, and this preference was expressed even when presented with narrowband, 1 kHz sweeps that crossed only a fraction of their excitatory receptive fields. This selectivity was also expressed in response to two tones delayed in time, termed two-tone facilitation (TTF). Direction-selective neurons showed a greatly facilitated response when a higher-frequency tone preceded a lower-frequency tone, simulating conditions in a downward sweep. The degree of temporal asymmetry in facilitation accurately predicted direction selectivity. When the spectral difference between the two tones was increased, the best delay also increased and could be used to predict a neuron's preferred sweep rate. To determine whether TTF alone created rate and direction selectivity, low- and high-frequency inhibitory sidebands, which can also shape selectivity, were eliminated from sweeps. In most cases, selectivity persisted. These results support the idea of spectral delay lines that produce an overlap and summation of excitatory inputs only when a dynamic stimulus traverses a receptive field in one direction at a specific velocity.

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Razak, Khaleel A., and Zoltan M. Fuzessery. "Neural Mechanisms Underlying Selectivity for the Rate and Direction of Frequency-Modulated Sweeps in the Auditory Cortex of the Pallid Bat." Journal of Neurophysiology 96, no. 3 (September 2006): 1303–19. http://dx.doi.org/10.1152/jn.00020.2006.

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Frequency-modulated (FM) sweeps are common in vocalizations, including human speech. Selectivity for FM sweep rate and direction is present in the auditory cortex of many species. The present study sought to determine the mechanisms underlying FM sweep selectivity in the auditory cortex of pallid bats. In the pallid bat inferior colliculus (IC), two mechanisms underlie selectivity for FM sweep rate. The first mechanism depends on duration tuning for tones that arises as a consequence of early inhibition generated by an excitatory tone. The second mechanism depends on a narrow band of delayed high-frequency inhibition. Direction selectivity depends on a broad band of early low-frequency inhibition. Here, the contributions of these mechanisms to cortical FM sweep selectivity were determined in pentobarbital-anesthetized pallid bats. We show that the majority of cortical neurons tuned to echolocation frequencies are selective for the downward direction and rate of FM sweeps. Unlike in IC neurons tuned in the echolocation range, duration tuning is rare in cortical neurons with similar tuning. As in the IC, consistent spectrotemporal differences exist between low- and high-frequency sidebands. A narrow band of delayed high-frequency inhibition is necessary for FM rate selectivity. Low-frequency inhibition has a broad bandwidth, early arrival time, and creates direction selectivity. Cortical neurons respond better to slower FM rates and exhibit broader rate tuning than IC neurons. Relative arrival time of high-frequency inhibition is slower in the cortex than in the IC. Thus whereas similar mechanisms shape direction selectivity of neurons tuned in the echolocation range in the IC and the cortex, only one of the two mechanisms underlying rate selectivity in the IC is present in the cortex.

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Yang, Fengming, Wenwen Wang, Bo Yan, Tao Hong, Yang Yang, Huacheng Zhu, Li Wu, and Kama Huang. "Sweep Frequency Heating based on Injection Locked Magnetron." Processes 7, no. 6 (June 5, 2019): 341. http://dx.doi.org/10.3390/pr7060341.

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Conventional microwave heating has serious problems such as non-uniform heating and low efficiency. A novel magnetron microwave sweep frequency heating method is proposed to improve microwave heating uniformity. In this method, the frequency-sweeping signal is injected into the magnetron by the injection frequency-locking technique, and the microwave sweep frequency heating of the magnetron is realized. In this paper, a complicated injection frequency locking system is given and analyzed and a multiphysics calculation model based on the finite element method for electromagnetic waves and heat transfer is established. The calculation of microwave sweep frequency heating is realized by the combination of COMSOL and MATLAB. The results show that the sweep frequency heating has an obvious superiority. An experiment is carried out to verify the simulation results. The simulation results are in agreement with the experimental data. Moreover, the effect of sweep bandwidth and sweep interval on heating uniformity is discussed.

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Villeneuve, Eric, Christophe Volat, and Sebastian Ghinet. "Numerical and Experimental Investigation of the Design of a Piezoelectric De-Icing System for Small Rotorcraft Part 2/3: Investigation of Transient Vibration during Frequency Sweeps and Optimal Piezoelectric Actuator Excitation." Aerospace 7, no. 5 (April 28, 2020): 49. http://dx.doi.org/10.3390/aerospace7050049.

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The objective of this research project is divided in four parts: (1) to design a piezoelectric actuator based de-icing system integrated to a flat plate experimental setup, develop a numerical model of the system and validate experimentally; (2) use the experimental setup to investigate actuator activation with frequency sweeps and transient vibration analysis; (3) add an ice layer to the numerical model, predict numerically stresses at ice breaking and validate experimentally; and (4) implement the concept to a blade structure for wind tunnel testing. This paper presents the second objective of this study, in which the experimental setup designed in the first phase of the project is used to study transient vibration occurring during frequency sweeps. Acceleration during different frequency sweeps was measured with an accelerometer on the flat plate setup. The results obtained showed that the vibration pattern was the same for the different sweep rate (in Hz/s) tested for a same sweep range. However, the amplitude of each resonant mode increased with a sweep rate decrease. Investigation of frequency sweeps performed around different resonant modes showed that as the frequency sweep rate tends towards zero, the amplitude of the mode tends toward the steady-state excitation amplitude value. Since no other transient effects were observed, this signifies that steady-state activation is the optimal excitation for a resonant mode. To validate this hypothesis, the flat plate was installed in a cold room where ice layers were accumulated. Frequency sweeps at high voltage were performed and a camera was used to record multiple pictures per second to determine the frequencies where breaking of the ice occur. Consequently, the resonant frequencies were determined from the transfer functions measured with the accelerometer versus the signal of excitation. Additional tests were performed in steady-state activation at those frequencies and the same breaking of the ice layer was obtained, resulting in the first ice breaking obtained in steady-state activation conditions as part of this research project. These results confirmed the conclusions obtained following the transient vibration investigation, but also demonstrated the drawbacks of steady-state activation, namely identifying resonant modes susceptible of creating ice breaking and locating with precision the frequencies of the modes, which change as the ice accumulates on the structure. Results also show that frequency sweeps, if designed properly, can be used as substitute to steady-state activation for the same results.

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Brown, Trecia A., and Robert V. Harrison. "Responses of Neurons in Chinchilla Auditory Cortex to Frequency-Modulated Tones." Journal of Neurophysiology 101, no. 4 (April 2009): 2017–29. http://dx.doi.org/10.1152/jn.90931.2008.

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Frequency-modulated (FM) stimuli have been used to explore the behavior of neurons in the auditory cortex of several animal models; however, the properties of FM-sensitive auditory cortical neurons in the chinchilla are still unknown. Single-unit responses to FM stimulation were obtained from the auditory cortex of anesthetized adult chinchillas ( Chinchilla laniger). Upward and downward linear FM sweeps spanning frequencies from 0.1 to 20 kHz were presented at speeds of 0.05 to 0.82 kHz/ms. Results indicated that >90% of sampled neurons were responsive to FM sweeps. The population preference was for upward FM sweeps and for medium to fast speeds (≥0.3 kHz/ms). Few units (3%) were selective for downward FM sweeps, whereas <22% of units preferred slow speeds (≤0.1 kHz/ms). Velocity preference and direction sensitivity were positively correlated for upward sweeps only ( r = 0.40, P = 0.0021, t-test). Three types of firing rate patterns were observed in the FM response peristimulus time histograms: a single peak at sweep onset/offset (“onset”) and a single peak (“late”) or multiple peaks (“burst”) during the sweep. “Late” units expressed the highest mean values for direction sensitivity and speed selectivity; “onset” units were selective only for direction and “burst” units were not selective for either direction or speed. The robust responsiveness of these neurons to FM sweeps suggests a functional role for FM detection such as the identification of FM sweeps present in vocalizations of other organisms within the chinchilla's natural environment.

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Yashiro, Ken'ichiro, Yoshihide Nishihara, and Sumio Ohkawa. "Ultrasonic Beam Scanning by Frequency Sweep." Japanese Journal of Applied Physics 26, S1 (January 1, 1987): 106. http://dx.doi.org/10.7567/jjaps.26s1.106.

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Ganguli, R. C., and Amitava Biswas. "Digital Frequency Synthesizer with Auto-Sweep." IETE Technical Review 2, no. 10 (October 1985): 345–48. http://dx.doi.org/10.1080/02564602.1985.11437842.

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Lin, Qi Feng, and Jin Hua Teng. "Application Research of Sweep Frequency in GMI Test." Advanced Materials Research 816-817 (September 2013): 285–88. http://dx.doi.org/10.4028/www.scientific.net/amr.816-817.285.

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Because of inefficiency of many tests needed in GMI research, this paper put forward the sweep frequency measurement method to implement the measurement of GMI effect under multi frequency at the same time in a single test. Experiments proved that the GMI effect curves which are measured by the sweep measurement method are consistent with other method's results, and the sweep frequency measurement method can greatly reduce the time of GMI test and improving the efficiency of the test.

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EJIRI, Akira, Yoshiyuki SHIMADA, Takuma YAMADA, Takuya OOSAKO, Yuichi TAKASE, and Hiroshi KASAHARA. "Relative Frequency Calibration for Fast Frequency Sweep Microwave Reflectometry." Plasma and Fusion Research 2 (2007): 040. http://dx.doi.org/10.1585/pfr.2.040.

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Martinez, Juan, Angel Belenguer, and Héctor Esteban. "Fast Frequency Sweep Technique Based on Segmentation for the Acceleration of the Electromagnetic Analysis of Microwave Devices." Applied Sciences 9, no. 6 (March 16, 2019): 1118. http://dx.doi.org/10.3390/app9061118.

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The characterization of communication devices in a certain frequency band can be accelerated if a fast frequency sweep technique is used instead of a discrete frequency sweep. Existing fast frequency sweep techniques are either complex or specific for a certain electromagnetic solver. In this work, a new fast frequency sweep method is proposed that consists in segmenting the device under analysis into simple building blocks. Each building block is characterized with a generalized (multimode) circuital matrix whose elements present a simple and flat frequency response that is interpolated using natural cubic splines with very few points. In this way, the response of each block along the whole frequency band is obtained efficiently and accurately with as many frequency points as desired. Then, the circuital matrices of all the blocks are cascaded and the circuital matrix of the whole device in obtained. The new fast frequency sweep was successfully applied to the analysis of different types of devices (all metallic rectangular waveguide filter, dielectric loaded rectangular waveguide filter, and substrate integrated waveguide filter). The computational times were reduced to 15% or 19%, depending on the device, when compared with a discrete frequency sweep using the same electromagnetic solver.

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Titova, E. E., B. V. Kozelov, F. Jiriček, J. Smilauer, A. G. Demekhov, and V. Yu Trakhtengerts. "Verification of the backward wave oscillator model of VLF chorus generation using data from MAGION 5 satellite." Annales Geophysicae 21, no. 5 (May 31, 2003): 1073–81. http://dx.doi.org/10.5194/angeo-21-1073-2003.

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Abstract. We present a detailed study of chorus emissions in the magnetosphere detected on board Magion 5, when the satellite was not far from the magnetic equator. We determine the frequency sweep rate of more than 8500 electromagnetic VLF chorus elements. These results are compared with the backward wave oscillator (BWO) regime of chorus generation. Comparison of the frequency sweep rate with the BWO model shows: (i) There is a correlation between the frequency sweep rates and the chorus amplitudes. The frequency sweep rate increases with chorus amplitude, in accordance with expectations from the BWO model; (ii) The chorus growth rate, estimated from the frequency sweep rate, is in accord with that inferred from the BWO generation mechanism; (iii) The BWO regime of chorus generation ensures the observed decrease in the frequency sweep rate of the chorus elements with increasing L-shell.Key words. Magnetospheric physics (VLF emissions, energetic particles) – Space plasma physics (wave-particle interactions)

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Qin, Ling, JingYu Wang, and Yu Sato. "Heterogeneous Neuronal Responses to Frequency-Modulated Tones in the Primary Auditory Cortex of Awake Cats." Journal of Neurophysiology 100, no. 3 (September 2008): 1622–34. http://dx.doi.org/10.1152/jn.90364.2008.

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Previous studies in anesthetized animals reported that the primary auditory cortex (A1) showed homogenous phasic responses to FM tones, namely a transient response to a particular instantaneous frequency when FM sweeps traversed a neuron's tone-evoked receptive field (TRF). Here, in awake cats, we report that A1 cells exhibit heterogeneous FM responses, consisting of three patterns. The first is continuous firing when a slow FM sweep traverses the receptive field of a cell with a sustained tonal response. The duration and amplitude of FM response decrease with increasing sweep speed. The second pattern is transient firing corresponding to the cell's phasic tonal response. This response could be evoked only by a fast FM sweep through the cell's TRF, suggesting a preference for fast FM. The third pattern was associated with the off response to pure tones and was composed of several discrete response peaks during slow FM stimulus. These peaks were not predictable from the cell's tonal response but reliably reflected the time when FM swept across specific frequencies. Our A1 samples often exhibited a complex response pattern, combining two or three of the basic patterns above, resulting in a heterogeneous response population. The diversity of FM responses suggests that A1 use multiple mechanisms to fully represent the whole range of FM parameters, including frequency extent, sweep speed, and direction.

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O'Neill, William E., and W. Owen Brimijoin. "Directional Selectivity for FM Sweeps in the Suprageniculate Nucleus of the Mustached Bat Medial Geniculate Body." Journal of Neurophysiology 88, no. 1 (July 1, 2002): 172–87. http://dx.doi.org/10.1152/jn.00966.2001.

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Mustached bats emit echolocation and communication calls containing both constant frequency (CF) and frequency-modulated (FM) components. Previously we found that 86% of neurons in the ventral division of the external nucleus of the inferior colliculus (ICXv) were directionally selective for linear FM sweeps and that selectivity was dependent on sweep rate. The ICXv projects to the suprageniculate nucleus (Sg) of the medial geniculate body. In this study, we isolated 37 single units in the Sg and measured their responses to best excitatory frequency (BEF) tones and linear 12-kHz upward and downward FM sweeps centered on the BEF. Sweeps were presented at durations of 30, 12, and 4 ms, yielding modulation rates of 400, 1,000, and 3,000 kHz/s. Spike count versus level functions were obtained at each modulation rate and compared with BEF controls. Sg units responded well to both tones and FM sweeps. BEFs clustered at 58 kHz, corresponding to the dominant CF component of the sonar signal. Spike count functions for both tones and sweeps were predominantly non-monotonic. FM directional selectivity was significant in 53–78% of the units, depending on modulation rate and level. Units were classified as up-selective (52%), down-selective(24%), or bi-directional ( non-selective, 16%); a few units (8%) showed preferences that were either rate-or level-dependent. Most units showed consistent directional preferences at all SPLs and modulation rates tested, but typically showed stronger selectivity at lower sweep rates. Directional preferences were attributable to suppression of activity by sweeps in the non-preferred direction (∼80% of units) and/or facilitation by sweeps in the preferred direction (∼20–30%). Latencies for BEF tones ranged from 4.9 to 25.7 ms. Latencies for FM sweeps typically varied linearly with sweep duration. Most FM latency-duration functions had slopes ranging from 0.4 to 0.6, suggesting that the responses were triggered by the BEF. Latencies for BEF tones and FM sweeps were significantly correlated in most Sg units, i.e., the response to FM was temporally related to the occurrence of the BEF in the FM sweep. FM latency declined relative to BEF latency as modulation rate increased, suggesting that at higher rates response is triggered by frequencies in the sweep preceding the BEF. We conclude that Sg and ICXv units have similar, though not identical, response properties. Sg units are predominantly upsweep selective and could respond to either or both the CF and FM components in biosonar signals in a number of echolocation scenarios, as well as to a variety of communication sounds.

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Zhang, Fu Quan, Yong Zhou Wang, Mei Chen, Mao Fang Huang, and Ri Zhong Zeng. "Study on Rheological Characterization of Uncured Natural Rubber with Different Initial Moisture Contents Dried by Microwave." Advanced Materials Research 998-999 (July 2014): 383–86. http://dx.doi.org/10.4028/www.scientific.net/amr.998-999.383.

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In this work, the rheological behavior of uncured natural rubber with different initial moisture contents dried by microwave was studied using RPA under frequency sweep and strain sweep modes. It can be seen from the results that the variation trend of viscous torque S`` versus sweep frequency kept with the trend of elastic torque S` versus sweep frequency. Moreover, the viscous torque S`` values were lower than those for elastic torque S`, a good linear relation curve was obtained by plotting elastic torque S` versus sweep frequency. The curve of storage shear modulus G` versus sweep strain presented a linear relationship, showed a linear viscoelastic behavior of uncured natural rubber with different initial moisture contents. This may be explained by the degradation of molecular chains of natural rubber and the van der waals forces between them.

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Insanally, Michele N., Badr F. Albanna, and Shaowen Bao. "Pulsed Noise Experience Disrupts Complex Sound Representations." Journal of Neurophysiology 103, no. 5 (May 2010): 2611–17. http://dx.doi.org/10.1152/jn.00872.2009.

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Cortical sound representations are adapted to the acoustic environment. Early exposure to exponential frequency-modulated (FM) sweeps results in more neurons selective to the experienced sounds. Here we examined the influence of pulsed noise experience on the development of sound representations in the primary auditory cortex (AI) of the rat. In naïve animals, FM sweep direction selectivity depends on the characteristic frequency (CF) of the neuron—low CF neurons tend to select for upward sweeps and high CF neurons for downward sweeps. Such a CF dependence was not observed in animals that had received weeklong exposure to pulsed noise in periods from postnatal day 8 (P8) to P15 or from P24 to P39. In addition, AI tonotopicity, tuning bandwidth, intensity threshold, tone-responsiveness, and sweep response magnitude were differentially affected by the noise experience depending on the exposure time windows. These results are consistent with previous findings of feature-dependent multiple sensitive periods. The different effects induced here by pulsed noise and previously by FM sweeps further indicate that plasticity in cortical complex sound representations is specific to the sensory input.

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Pongrac, Blaž, Denis Đonlagic, Matej Njegovec, and Dušan Gleich. "THz Signal Generator Using a Single DFB Laser Diode and the Unbalanced Optical Fiber Interferometer." Sensors 20, no. 17 (August 28, 2020): 4862. http://dx.doi.org/10.3390/s20174862.

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This paper presents a frequency-modulated optical signal generator in the THz band. The proposed method is based on a fast optical frequency sweep of a single narrowband laser diode used together with an optical fiber interferometer. The optical frequency sweep using a single laser diode is achieved by generating short current pulses with a high amplitude, which are driving the laser diode. Theoretical analysis showed that the modulation frequency could be changed by the optical path difference of the interferometer or optical frequency sweep rate of a laser diode. The efficiency of the optical signal generator with Michelson and Fabry–Perot interferometers is theoretically analyzed and experimentally evaluated for three different scenarios. Interferometers with different optical path differences and a fixed optical frequency sweep rate were used in the first scenario. Different optical frequency sweep rates and fixed optical path differences of the interferometers were used in the second scenario. This paper presents a method for optical chirp generation using a programmable current pulse waveform, which drives a laser diode to achieve nonlinear optical sweep with a fixed optical path difference of the interferometer. The experimental results showed that the proposed signals could be generated within a microwave (1–30 GHz) and THz band (0.1–0.3 THz).

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Mileusnic, Mladen, Branislav Pavic, Verica Marinkovic-Nedelicki, Predrag Petrovic, Dragan Mitic, and Aleksandar Lebl. "Analysis of jamming successfulness against RCIED activation with the emphasis on sweep jamming." Facta universitatis - series: Electronics and Energetics 32, no. 2 (2019): 211–29. http://dx.doi.org/10.2298/fuee1902211m.

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In this paper we first briefly compare the performances of active jamming remote controlled improvised explosive devices activation using wide-band noise and frequency sweep signal. Frequency sweep is the most widely used technique intended for active jamming and we analyze its characteristics: 1) sweep speed, 2) conditions for certainly successful jamming, 3) successful jamming probability if jamming is not certainly successful, and 4) step of frequency change when frequency sweep is applied. The separate paper section is devoted to the successful jamming probability calculation in general. The attention is also paid to jamming probability determination when starting and ending sweep signal frequencies are varied. The initial research has been upgraded and extended. The presented results refer to jamming equipment development in IRITEL, but it is important to add that they are also applicable to the other similar jamming systems realizations.

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Trujillo, Michael, and Khaleel A. Razak. "Altered cortical spectrotemporal processing with age-related hearing loss." Journal of Neurophysiology 110, no. 12 (December 15, 2013): 2873–86. http://dx.doi.org/10.1152/jn.00423.2013.

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Presbycusis (age-related hearing loss) is a prevalent disability associated with aging that impairs spectrotemporal processing, but the mechanisms of such changes remain unclear. The goal of this study was to quantify cortical responses to frequency-modulated (FM) sweeps in a mouse model of presbycusis. Previous studies showed that cortical neurons in young mice are selective for the rate of frequency change in FM sweeps. Here single-unit data on cortical selectivity and response variability to FM sweeps of either direction and different rates (0.08–20 kHz/ms) were compared across young (1–3 mo), middle-aged (6–8 mo), and old (14–20 mo) groups. Three main findings are reported. First, there is a reduction in FM rate selectivity in the old group. Second, there is a slowing of the sweep rates at which neurons likely provide best detection and discrimination of sweep rates. Third, there is an increase in trial-to-trial variability in the magnitude and timing of spikes in response to sweeps. These changes were only observed in neurons that were selective for the fast or intermediate range of sweep rates and not in neurons that preferred slow sweeps or were nonselective. Increased variability of response magnitude, but not changes in temporal fidelity or selectivity, was seen even in the middle-aged group. The results show that spectrotemporal processing becomes slow and noisy with presbycusis in specific types of neurons, suggesting receptive field mechanisms that are altered. These data suggest neural correlates of presbycusis-related reduction in the ability of humans to process rapid spectrotemporal changes.

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Peterzell, David H., and Anthony M. Norcia. "Spatial frequency masking with the sweep-VEP." Vision Research 37, no. 17 (September 1997): 2349–59. http://dx.doi.org/10.1016/s0042-6989(97)00046-1.

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Farle, Ortwin, Markus Lösch, and Romanus Dyczij-Edlinger. "Efficient Fast Frequency Sweep Without Nonphysical Resonances." Electromagnetics 30, no. 1-2 (March 9, 2010): 51–68. http://dx.doi.org/10.1080/02726340903485307.

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Skorheim, Steven, Khaleel Razak, and Maxim Bazhenov. "Network Models of Frequency Modulated Sweep Detection." PLoS ONE 9, no. 12 (December 16, 2014): e115196. http://dx.doi.org/10.1371/journal.pone.0115196.

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Singh, Piyush K., Johannes M. Soulages, and Randy H. Ewoldt. "Frequency-sweep medium-amplitude oscillatory shear (MAOS)." Journal of Rheology 62, no. 1 (January 2018): 277–93. http://dx.doi.org/10.1122/1.4999795.

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Barghi, Neda, and Christian Schlötterer. "Distinct Patterns of Selective Sweep and Polygenic Adaptation in Evolve and Resequence Studies." Genome Biology and Evolution 12, no. 6 (April 18, 2020): 890–904. http://dx.doi.org/10.1093/gbe/evaa073.

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Abstract In molecular population genetics, adaptation is typically thought to occur via selective sweeps, where targets of selection have independent effects on the phenotype and rise to fixation, whereas in quantitative genetics, many loci contribute to the phenotype and subtle frequency changes occur at many loci during polygenic adaptation. The sweep model makes specific predictions about frequency changes of beneficial alleles and many test statistics have been developed to detect such selection signatures. Despite polygenic adaptation is probably the prevalent mode of adaptation, because of the traditional focus on the phenotype, we are lacking a solid understanding of the similarities and differences of selection signatures under the two models. Recent theoretical and empirical studies have shown that both selective sweep and polygenic adaptation models could result in a sweep-like genomic signature; therefore, additional criteria are needed to distinguish the two models. With replicated populations and time series data, experimental evolution studies have the potential to identify the underlying model of adaptation. Using the framework of experimental evolution, we performed computer simulations to study the pattern of selected alleles for two models: 1) adaptation of a trait via independent beneficial mutations that are conditioned for fixation, that is, selective sweep model and 2) trait optimum model (polygenic adaptation), that is adaptation of a quantitative trait under stabilizing selection after a sudden shift in trait optimum. We identify several distinct patterns of selective sweep and trait optimum models in populations of different sizes. These features could provide the foundation for development of quantitative approaches to differentiate the two models.

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Liu, Jia Qi, Ling Tian, Wei Hong, and Jian Ye Zhang. "Design of C-Band Wideband Sweep Frequency Source." Applied Mechanics and Materials 130-134 (October 2011): 3263–66. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.3263.

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This paper presents the design and fabrication of a compact 4-8GHz sweep frequency source at C-band with a hybrid frequency synthesizer technology. With DDS used as PLL’s reference, the frequency step size is as small as 3×10-4 Hz and the measured 1 kHz offset phase noise is-91.79dBc/Hz at 4GHz. This frequency sweep source has advantages of wide bandwidth, low phase noise, small frequency step size, low spurious, fast tuning speed, small size and low power consumption. So it is suitable for wireless hand-held test equipment and communication equipment.

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Gao, Shuyuan, Rongyi Ji, Yao Li, Chun Liu, Junkai Shi, Yingling Pan, and Weihu Zhou. "Compensation of Frequency Drift in Frequency-Sweep Polarization-Modulation Ranging System." Applied Sciences 9, no. 6 (March 25, 2019): 1243. http://dx.doi.org/10.3390/app9061243.

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In frequency-sweep polarization-modulation ranging, distance is determined by the frequency of modulated waves and the corresponding wavelength multiple when emitted and returned waves are in phase. However, measurement of the frequency and the wavelength multiple is affected by thermally induced phase delay of the polarized wave. In this article we systematically discuss the principle of the ranging method and analyze the influences of thermally induced phase delay. New approaches to measurement are proposed to eliminate the impact on frequency and the wavelength multiple. Theoretical analysis and experimental results proved the efficiency and applicability of the methods.

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Wang, Yong Zhou, Fu Quan Zhang, Mei Chen, Ming Zhe Lv, and Hong Hai Huang. "Study on Properties and Cross-Linking Structure of NR Dried by Microwave." Advanced Materials Research 335-336 (September 2011): 442–45. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.442.

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In this work, the cross-linking density and frequency sweep, temperature sweep of NR dried by microwave were tested by using nuclear magnetic resonance spectrometer (NMR) and rubber process analyzer (RPA), respectively. And the test results were compared with those of NR dried by hot-air. The results showed that the cross-linking density and A(Mc) for NR dried by microwave were bigger than those for NR dried by hot-air, but the A(T2) of latter was bigger; the frequency sweep results showed that the elastic modulus of NR dried by hot-air increased slower with the increase of frequency than those of NR dried by microwave , and the tanδ of NR dried by hot-air decreased with the increase of frequency slower than those of NR dried by microwave in low frequency phase, respectively; the temperature sweep results showed that the elastic modulus of NR dried by hot air were smaller compared with those of NR dried by microwave in the entire scanning process, but, the tanδ value of former was bigger.

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Indrawijaya, R., R. Sariningrum, B. Edi Sukoco, and D. Muliawandana. "Fractional-N PLL Synthesizer for FMCW Signal Generator with Dual-Mode Modulation Pattern." Jurnal Elektronika dan Telekomunikasi 18, no. 2 (December 28, 2018): 46. http://dx.doi.org/10.14203/jet.v18.46-52.

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Radar signal generator is a critical component in radar system as it determines the best achievable resolution. Single chip Fractional-N PLL synthesizer with built-in VCO and sweep modulator become more popular as Frequency Modulated Continuous Wave (FMCW) signal generator due to the simplicity and overall cost reduction. This paper presents a realization process and experimental result of dual-mode modulation pattern FMCW signal generator using HMC769LP6CE PLL. The PLL is controlled by ATMega328 microcontroller and Altera EPM240T100C5 CPLD to operate in two difference mode: 1-way sweep mode and 2-way sweep mode. The PLL is programmed with four different sweep bandwidth from 6.75–54 MHz for different range and resolution radar purpose. The performance of FMCW signal generator is measured using the output of passband signal spectrum. The experimental results indicate that the PLL-VCO with 2-way sweep mode has clearer frequency passband compared to 1-way sweep mode.

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Aithal, Venkatesh, Joseph Kei, Carlie Driscoll, Andrew Swanston, Katrina Roberts, Michio Murakoshi, and Hiroshi Wada. "Normative Sweep Frequency Impedance Measures in Healthy Neonates." Journal of the American Academy of Audiology 25, no. 04 (April 2014): 343–54. http://dx.doi.org/10.3766/jaaa.25.4.6.

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Background: Diagnosing middle ear disorders in neonates is a challenging task for both audiologists and otolaryngologists. Although high-frequency (1000 Hz) tympanometry and acoustic stapedial reflex tests are useful in diagnosing middle ear problems in this age group, they do not provide information about the dynamics of the middle ear in terms of its resonance frequency (RF) and mobility. The sweep frequency impedance (SFI) test can provide this information, which may assist in the diagnosis of middle ear dysfunction in neonates. Purpose: This study aimed to investigate the feasibility of testing neonates using the SFI technique, establish normative SFI data for RF and mobility of the middle ear in terms of changes in sound pressure level (ΔSPL in dB), and describe the dynamics of the middle ear in healthy Australian neonates. Study Sample: A prospective sample of 100 neonates (58 males, 42 females) with a mean gestational age of 39.3 wk (SD = 1.3 wk; range = 38–42 wk), who passed all three tests, namely, automated auditory brainstem response, transient evoked otoacoustic emissions, and 1000 Hz tympanometry, were included in this study. Data Collection and Analysis: A SFI research prototype was used to collect the data. First, the SPL in the ear canal was measured as a probe-tone frequency was swept from 100–2000 Hz with the ear canal static pressure held constant at 200 daPa. Then, this measurement was repeated with the static pressure reduced in 50 daPa steps to –200 daPa. Additional measurement was also performed at the static pressure, where the peak of the 1000 Hz tympanogram occurred. A graph showing the variation of SPL against frequency at all static pressures was plotted. From this graph, the RF and ΔSPL at tympanometric peak pressure (TPP) were determined. Descriptive statistics and an analysis of variance (ANOVA) were applied to the RF and ΔSPL data with gender and ear as independent variables. Results: The results showed two resonance regions of the outer/middle ear with the high RF (mean = 1236 Hz; 90% range: 830–1518 Hz) being approximately equal to four times that of the low RF (mean = 287 Hz; 90% range = 209–420 Hz). The low RF was more easily identifiable than the high RF. The ΔSPL at the low RF (mean = 8.2 dB; 90% range = 3.4–13 dB) was greater than that at the high RF (mean = 5.0 dB; 90% range = 1.5–8.1 dB). There were no significant differences or interactions between genders and ears. Conclusion: The study showed that the SFI is a feasible test of middle ear function in neonates. The SFI results revealed two regions of resonance with the lower resonance (287 Hz) possibly related to the movements of the outer ear canal wall and higher resonance (1236 Hz) related to the resonance of the middle ear. The normative data developed in this study will be useful in evaluating outer and middle ear function in neonates.

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Hara, H., M. Ikeya, T. Nakajima, and Y. Nishiwaki. "Frequency Sweep ESR Spectrometer for Dosimetry and Dating." Radiation Protection Dosimetry 34, no. 1-4 (December 1, 1990): 335–37. http://dx.doi.org/10.1093/rpd/34.1-4.335.

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40

Lee, Judy, Loïc Hallez, Francis Touyeras, Muthupandian Ashokkumar, and Jean-Yves Hihn. "Influence of frequency sweep on sonochemiluminescence and sonoluminescence." Ultrasonics Sonochemistry 64 (June 2020): 105047. http://dx.doi.org/10.1016/j.ultsonch.2020.105047.

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41

Minissale, Marco, Thomas Zanon-Willette, Ivan Prokhorov, Hadj Elandaloussi, and Christof Janssen. "Nonlinear Frequency-Sweep Correction of Tunable Electromagnetic Sources." IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 65, no. 8 (August 2018): 1487–91. http://dx.doi.org/10.1109/tuffc.2018.2843183.

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42

Soliman, E. A. "Rapid frequency sweep technique for MoM planar solvers." IEE Proceedings - Microwaves, Antennas and Propagation 151, no. 4 (2004): 277. http://dx.doi.org/10.1049/ip-map:20040646.

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43

Comisarow, Melvin B., and Alan G. Marshall. "Frequency-sweep fourier tranform ion cyclotron resonance spectroscopy." Journal of Mass Spectrometry 31, no. 6 (April 13, 2007): 588–89. http://dx.doi.org/10.1002/jms.1190310603.

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44

Troger, Joerg, Luc Thévenaz, and Philippe Robert. "Frequency-sweep generation by resonant self-injection locking." Optics Letters 24, no. 21 (November 1, 1999): 1493. http://dx.doi.org/10.1364/ol.24.001493.

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45

Hara, H., M. Ikeya, T. Nakajima, and Y. Nishiwaki. "Frequency Sweep ESR Spectrometer for Dosimetry and Dating." Radiation Protection Dosimetry 34, no. 1-4 (December 1, 1990): 335–37. http://dx.doi.org/10.1093/oxfordjournals.rpd.a080916.

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Skorheim, Steven, Khaleel Razak, and Maxim Bazhenov. "Correction: Network Models of Frequency Modulated Sweep Detection." PLOS ONE 10, no. 8 (August 14, 2015): e0136010. http://dx.doi.org/10.1371/journal.pone.0136010.

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47

Smit, H. W., N. A. M. Schellart, and C. A. Grimbergen. "Gain-controlled frequency sweep generator for auditory stimulation." Medical & Biological Engineering & Computing 24, no. 4 (July 1986): 442–46. http://dx.doi.org/10.1007/bf02442702.

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48

Hara, Hidemoto, and Motoji Ikeya. "Frequency-sweep ESR spectrometer for dosimetry and dating." International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes 40, no. 10-12 (January 1989): 841–43. http://dx.doi.org/10.1016/0883-2889(89)90004-x.

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Li, Xiao‐Ping. "Decomposition of vibroseis data by the multiple filter technique." GEOPHYSICS 62, no. 3 (May 1997): 980–91. http://dx.doi.org/10.1190/1.1444204.

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A harmonically distorted vibroseis signal is decomposed using the “multiple filter technique” in a similar manner as the wavelet transform. The 1-D vibroseis signal is transformed into a 2-D function of time and frequency. The procedure consists of applying a family of narrow Gaussian filters whose center frequencies are close to the instantaneous frequencies of the harmonically distorted vibroseis signal. As a result of this decomposition, an envelope trace is obtained for every center frequency. For a linear fundamental (pilot) sweep, the fundamental sweep and its harmonic distortions have different arrival times in the decomposed envelope trace. An accurate analysis of the harmonic distortion can be carried out using the amplitudes along the slopes of the instantaneous frequency defined for the linear fundamental sweep and its harmonic distortions. Plotting the contoured amplitudes of each envelope trace on a frequency‐versus‐time scale yields the amplitude distribution between the fundamental sweep and its harmonic distortions. They represent the frequency content of the uncorrelated vibroseis signal and can be used to examine the interaction and leakage of the signal and its harmonics. Similarly, the correlation noise, the so‐called “ghost sweep” in the correlated vibroseis data, can be decomposed with this technique. The method is applied to synthetic, harmonically distorted, vibroseis signals and to a real vibroseis vertical seismic profile (VSP) data set.

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Harris, Alexandre M., and Michael DeGiorgio. "A Likelihood Approach for Uncovering Selective Sweep Signatures from Haplotype Data." Molecular Biology and Evolution 37, no. 10 (May 11, 2020): 3023–46. http://dx.doi.org/10.1093/molbev/msaa115.

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Abstract Selective sweeps are frequent and varied signatures in the genomes of natural populations, and detecting them is consequently important in understanding mechanisms of adaptation by natural selection. Following a selective sweep, haplotypic diversity surrounding the site under selection decreases, and this deviation from the background pattern of variation can be applied to identify sweeps. Multiple methods exist to locate selective sweeps in the genome from haplotype data, but none leverages the power of a model-based approach to make their inference. Here, we propose a likelihood ratio test statistic T to probe whole-genome polymorphism data sets for selective sweep signatures. Our framework uses a simple but powerful model of haplotype frequency spectrum distortion to find sweeps and additionally make an inference on the number of presently sweeping haplotypes in a population. We found that the T statistic is suitable for detecting both hard and soft sweeps across a variety of demographic models, selection strengths, and ages of the beneficial allele. Accordingly, we applied the T statistic to variant calls from European and sub-Saharan African human populations, yielding primarily literature-supported candidates, including LCT, RSPH3, and ZNF211 in CEU, SYT1, RGS18, and NNT in YRI, and HLA genes in both populations. We also searched for sweep signatures in Drosophila melanogaster, finding expected candidates at Ace, Uhg1, and Pimet. Finally, we provide open-source software to compute the T statistic and the inferred number of presently sweeping haplotypes from whole-genome data.

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Journal articles on the topic 'Sweep frequency'

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