Changes in EEG power spectra during dexmedetomidine anaesthesia. Summary. Comparison between agents revealed a stronger attenuation of cortical power by isoflurane compared with dexmedetomidine (over the 76–200 Hz range) or propofol (over the 30–200 Hz range).13 The most likely explanation for the steeper concentration-effect slope of isoflurane is that this agent, like other volatile anaesthetics, has additional molecular targets, notably the two-pore potassium channels and the NMDA receptor.34. A modem is classified as low speed if data rate handled is. The SNR for a multiple echo (TS = −40 dB, The effect of sea thermal noise and receiver noise on SNR for a target with, Absorption attenuation at 38 kHz and 200 kHz for North and South seas and four seasons computed by using the temperature profiles shown in Figure, Deviations of two-way absorption attenuations (, Effects of Noise and Absorption on High Frequency Measurements of Acoustic-Backscatter from Fish, Tokyo University of Marine Science and Technology, 4-5-7 Kounan, Minato, Tokyo 108-8477, Japan, M. Furusawa, “Designing quantitative echo sounders,”, R. J. Korneliussen, N. Diner, E. Ona, L. Berger, and P. G. Fernandes, “Proposals for the collection of multifrequency acoustic data,”, A. M. Kaltenberg and K. J. Benoit-Bird, “Intra-patch clustering in mysid swarms revealed through multifrequency acoustics,”, D. Lemon, G. Borstad, L. Brown, and P. Johnston, “Moored multiple-frequency sonar for long-term continuous observations of zooplankton and fish,”, R. J. Korneliussen and E. Ona, “An operational system for processing and visualizing multi-frequency acoustic data,”, “The SIMFAMI project: species identification methods from acoustic multifrequency information,”, Y. Takao, K. Sawada, Y. Miyanohana, T. Okumura, M. Furusawa, and D. Hwang, “Noise characteristics of Japanese fisheries’ research vessels,”, R. H. Mellen, “The thermal-noise limit in the detection of underwater acoustic signals,”, V. O. Knudsen, R. S. Alford, and J. W. Emling, “Underwater ambient noise,”, G. M. Wenz, “Acoustic ambient noise in the ocean: spectra and sources,”, M. Furusawa, “Section and total scattering strengths of individual fish school,”, F. E. Tichy, H. Solli, and H. Klaveness, “Non-linear effects in a 200-kHz sound beam and the consequences for target-strength measurement,”, R. E. Francois and G. R. Garrison, “Sound absorption based on ocean measurements. The multiple echo from a fish school is expressed aswhere is the pressure of multiple echo, is the pulse duration, is the equivalent beam angle in steradians, and is the distribution density of fish or any animals in m−3. From the above reasoning, the signal for the basis of the SNR should be single scatterer echoes. Using N′ profiles, the attenuation variations at N′ from the fixed characteristics at N at six frequenciesare calculated. … Decreased EEG coherence between distinct areas of the cerebral cortex during anaesthesia is interpreted as a sign of impaired neural communication, one of the proposed mechanisms by which general anaesthetics impair consciousness.1 How then, can the present finding of increased thalamocortical coherence in the delta band be reconciled with the substantial literature reporting decreased EEG coherence during anaesthesia?17 We see three explanatory elements. A similar analysis of coherence for the previously published propofol data12 also revealed an increase in delta coherence at the two propofol concentrations causing unconsciousness (9 µg ml−1 and 12 µg ml−1) (data not shown). The above active low pass filter circuit does not provide more than unity gain. Original profiles in [. Review articles are excluded from this waiver policy. the electrodes are all referred to one single electrode, the reference, that hopefully has little brain activity in it). In this study, the high‐frequency attenuation of upsweep was considered in the construction of the input wavelet for the synthetic seismogram in an area where the Vibroseis technique was used. Furthermore, the effect of dexmedetomidine on cortex and thalamus is of similar magnitude, in contrast to both isoflurane and propofol, which exerted a stronger effect on the thalamus. This is equivalent to computing the regression using 0, 0.33, 0.67, 1.00 and 1.33 for concentrations for the two i.v. Second, the sedative-hypnotic effect of dexmedetomidine is less intense than that of propofol or isoflurane, as revealed by the preserved ability to be awakened by verbal commands during deep sedation.14 If anaesthetic action depends on impairment of high-frequency rhythms, then the slope of the concentration-dependent attenuation of high-frequency thalamocortical rhythms by dexmedetomidine should be less than that of propofol or isoflurane. Conclusions. The advent of communications satellites in the late 1960's and early 1970's brought a change of philosophy about long-distance communications. The difference in latitudes of South and North in Figure 3 is 12° and is too large for our common practice. By the present modification, along with the slight modification for noise expression, (1), the SNR expression has become more appropriate for quantitative purposes and the frequency dependence has become simple and can be clearly understood. Bottom panels show power spectra obtained from one animal for cortex and thalamus. For Permissions, please email: email@example.com, http://www2.sas.com/proceedings/sugi31/187-31.pdf, Copyright © 2021 The British Journal of Anaesthesia Ltd. A test probe is a physical device used to connect electronic test equipment to a device under test (DUT). The neurophysiological role of cortical fast rhythms in attentional and cognitive processes is well documented.35 There is also evidence that these rhythms may be involved in conscious perception. On EEG coherence is of current interest anaesthetic action large for our common practice frequency 30–200! 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