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The following is not an answer to the original question: "Are Gram negative bacteria classified as such because of their negative membrane potential?" but to the questions later in the text. Usually the membrane potential is given for the inner cytosolic part and the extracellular space, for E. Coli it is around -120 mV; see also this article. Due to the ...


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Short answer The distinction between Gram positive (Gram+) and negative bacteria (Gram-) has absolutely nothing to do with membrane potentials; it is all about the Gram staining procedure. Background The Gram staining was named after the Danish bacteriologist Hans Christian Gram, who originally devised it in 1882 (Gram, 1884). Gram staining is a common ...


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Both Na+ and K+ will move according to the electrochemical gradient. Given that K+ leaky channels are ever present, the cell is already around its K+ equilibrium. If you introduce leaky Na+ channel and remove the pumps, eventually the cell will be nothing more than a passive membrane and it will adopt the same concentrations of ions as the extracellular ...


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ERPs are typically analyzed in terms of amplitude and latency. FFT is not really an option; it doesn't make sense. There may be some applications where it may be useful, but these are quite specific. For example, if repeated stimuli are presented and you are not averaging them, but you are collection an EEG, then FFT may help you to deduce whether stimulus ...


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Event-related potentials are an issue in many aspects of physiology, not just in EEG analysis, so this answer is more general. The main problem is that electrical or other signals that are associated with some "event" are typically much lower in magnitude than the background noise in the system being examined. Electrocardiograms are the exception in this ...


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EEG 10-20 system. source: Wikipedia How many actual channels are there? 21 in the figure, i.e., the number of active electrodes. What's the difference between reference and active channels? The active electrode is the electrode under investigation. Basically this is arbitrary. Consider electrode F2 and F3. When you measure the ...


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Fast-Fourier Transform (FFT) transforms a signal from the time domain into the frequency domain. Basically, any time-dependent signal can be broken down in a collection of sinusoids. In this way, lengthy and noisy EEG recordings can be conveniently plotted in a frequency power-spectrum. By doing so, hidden features can become apparent. By adding all the ...


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Any periodic waveform can be produced by adding up a series of sin waves of the appropriate frequency and amplitude. The FFT looks at a complex waveform and calculates those frequencies and amplitudes. The result is a new curve which plots amplitude vs frequency. Thus, it transforms the signal from the time domain into the frequency domain. I don't have ...


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So, are repetitions wanted in this kind of experiment? Yes: repetitions reduce random noise and increase the chance to tell artifact from response. Adaptation is a serious issue, typically becoming apparent by decreasing amplitudes, or even skipped responses. Reading the existing literature and/or performing experiments with various stimulus intervals ...



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