Low amplitude signal

If this conductance Is measured with an alternating, low amplitude signal Vm, of frequency % (from the same or another pair of electrodes In the sample cell) we see In the current frequency components which are not present In the signal sources ... 

The most obvious finding is the low amplitude signals being sensed in the VF and VT-1 zones, and that the ventricular escape is barely 20 b.p.m. with complete heart block. The low amplitude signals are caused by a loose set screw in the pacing/sensing lead port. These potentials result because the loose set screw intermittently makes and breaks contact with the lead. These potentials also inhibit pacing. Note the lack of these potentials on the shock EGM. 

These non-steady state techniques are based on the application of a perturbation to a system in equilibrium or in a steady state, and on the later study of the relaxation of the system. As the different elementary processes which intervene in the corrosion phenomenon have different relaxation constants, a low amplitude signal with a wide range offrequencies is used as pertmbing signal, which makes it possible to induce a linear response from the system. The response of the system will be the sum of the contributions of each elementary process, as each of them relaxes exponentially over time with a characteristic time constant. 

Linear (resistance) polarization, hi the realization of a polarization curve, the working electrode reaches high potential values causing a strong irreversible dissolution of the material. Thus, when attempts are made to evaluate the change in the corrosion rate over time of a metal under a uniform corrosion process, under control for activation, another type of non-destructive experiment is employed, namely the measurement of resistance to polarization. This is also a steady state technique and it is based on the application of a low amplitude signal of direct current around the corrosion potential, ensuring that the material continues in a situation of equilibrium. 

In an EIS experiment, a low amplitude (5 to 10 mV peak-to-peak) sine wave potential signal is superimposed on a fixed DC potential applied to an electrochemical system. Based on Ohm s law, the impedance can be computed from the applied sinusoidal potential and the measured sinusoidal current. As the sinusoidal potential and current will... 

The phase delay A(nwE) and modulation ratio M(na>E) information of the high-frequency signals is transferred to low-frequency signals by amplitude modulation (cross-correlation) of r.(t) and Iff) with a periodic train of pulses C(f) given by Ref. 29. 

Thus we have reduced this problem to the form of conventional SR (see Section II.C) with only a renormalized effective amplitude for the input signal Aeff [cf Eq. 9)] and the function M() replaced by its derivative M (< >) in the first term on the right hand side. By analogy with standard SR, the SNR for heterodyning can be characterized by the ratio R of the low-frequency signal in the intensity of the transmitted radiation, given by 4 (T x(H) 2, to the value of the power spectrum Q(0 (ll) [with Q (Q) given by (7)—(8)]. The susceptibility of the system can be easily calculated and takes the form... 

As discussed in Sect. 2.2.2, FMM images can lose the material contrast when the sample stiffness exceeds the stiffness of the cantilever. In addition, the net signal contains friction effects because of the cantilever bending and the sample indentation. Furthermore, in liquid samples, capillary forces dominate the response at low frequencies [ 127]. These drawbacks can be overcome by operating the microscope above the contact resonance frequencies. In the so-called con-tact-mode scanning local-acceleration microscope the cantilever oscillates at very low amplitudes of ca. 0.1 nm which still provides strong enough contrast with respect to the mechanical properties [122]. Since the response of the canti-... 

The numerical results are consistent with the result of an experiment in which the ion cyclotron orbit sizes of a methane (CHi, ) and benzene (C6H6 ) mixture of ions were varied. In the control experiment, the two ions were excited by low amplitude consecutive RF burst pulses of varied time. The signal ratio was essentially constant over the range of orbits for which signals were detectable. In contrast, for a chirp from 10 kHz to 2 Mhz at 2.094 kHz/usee of varied amplitude, the abundance ratio of CH t/C6H6t decreased from about 90 to about 10 as the orbit size was increased, indicating loss of the lighter ion. 

Derivative Detection of EPR Transition. The EPR spectrum is usually displayed as the first derivative of the absorption y"(H), because the nonresonant low-frequency and low-amplitude RF modulation (co1/ 2% = typically 100 kHz) applied to the coils near the magnet is detected by a rectifier in addition to the drop in microwave power level due to the RF resonant absorption (typically co0/27c = 9.1 GHz if H0 = 0.34T) The signal is processed by a phase-sensitive circuit, which detects a back-and-forth sweep across resonance in small magnetic field increments (relative to the DC field and to the width of the measured spectrum), thus generating a response df /dH (see Fig. 11.60). 

Electrochemical noise consists of low-frequency, low-amplitude fluctuations of current and potential due to electrochemical activity associated with corrosion processes. ECN occurs primarily at frequencies less than 10 Hz. Current noise is associated with discrete dissolution events that occur on a metal surface, while potential noise is produced by the action of current noise on an interfacial impedance (140). To evaluate corrosion processes, potential noise, current noise, or both may be monitored. No external electrical signal need be applied to the electrode under study. As a result, ECN measurements are essentially passive, and the experimenter need only listen to the noise to gather information. 

Tlie capacitive nature of the adsorption pseudocapacitance can be further illustrated by considering its ac response. Let us assume that a low amplitude sinusoidal voltage signal is applied to a system at equilibrium ... 

Different types of set-up have been reported in the literature. A typical transient absorption set-up with a continuum probe and subpicosecond time resolution, which can be used with laser pulses of a few hundred femtoseconds of duration, is shown in Fig. 7.15. The sample is excited by the pump pulses P. The pump flu-ence (number of photons per cm ) is set to be large enough to obtain an appreciable population of the excited state, which however can be small when an excitation source of high repetition rate is used (Ti-sapphire femtosecond lasers run at 1 kHz) because it allows fast accumulation of weak amplitude signals. With low repetition lasers (10 Hz) the excitation fluence should be dose to the saturation fluence ( l/ca, where (7 is the absorption cross section of the solute at the pump wave-... 

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