Modulation voltage

Triangular voltage waveform of fixed amplitude Variable frequency and modulated voltage output (V/f) as desired. 

The measured Auger signal is proportional to the number of atoms sampled. In the derivative mode of data acquisition this is frequently not the case, for example, if an inappropriate modulation voltage is used or if the line shape has... 

Neal AP, Yuan Y, Atchison WD (2010) Allethrin differentially modulates voltage-gated calcium channel subtypes in rat PC12 cells. Toxicol Sci 116 604—613... 

Scans based on resonant ejection may either be carried out in a forward, i.e., from low to high mass, or a reverse manner. This allows for the selective storage of ions of a certain m/z value by elimination of ions below and above that m/z value from the trap. Thus, it can serve for precursor ion selection in tandem MS experminents. [156,158] Axial excitation can also be used to cause collision-induced dissociation (CID) of the ions as a result of numerous low-energy collisions with the helium buffer gas that is present in the trap in order to dampen the ion motion. [150,156] A substantial increase of the mass range is realized by reduction of both the RF frequency of the modulation voltage and the physical size of theQIT. [154,159,160]... 

Ion trapping devices are sensitive to overload because of the detrimental effects of coulombic repulsion on ion trajectories. The maximum number of ions that can be stored in a QTT is about 10 -10, but it reduces to about 10 -10 if unit mass resolution in an RF scan is desired. Axial modulation, a sub-type of resonant ejection, allows to increase the number of ions stored in the QIT by one order of magnitude while maintaining unit mass resolution. [160,161] During the RF scan, the modulation voltage with a fixed amplitude and frequency is applied between the end caps. Its frequency is chosen slightly below V2 of the fundamental RF frequency, because for Pz < 1, e.g., = 0.98, we have z = (0 + 0.98/2) = 0.49 x... 

At the stability boundary, ion motion is in resonance with this modulation voltage, and thus ion ejection is facilitated. Axial modulation basically improves the mass-selective instability mode of operation. 

A variety of toxins that modulate voltage-gated sodium channels have been used to probe channel function. They can be classified on the basis of five discrete binding sites (Table 1). These binding sites are commonly found on all a-subunits and are being characterized at the molecular level. The sensitivity to the puffer fish poison tetrodotoxin (TTX) has been used to subdivide voltage-gated sodium channels (Table 3). 

Figure 14.4 Auger KVV carbon peak in (a) a thick graphite layer covering a carbide (b) /J-WC, film with <41 mol% carbon (c) a /i-WC, v film with about 50 mol% carbon. Spectra were acquired with a retarding field analyser in the derivative mode, using a grazing incidence electron gun, with primary beam energy of 2.5 keV the modulation voltage was...

IET line widths are determined by thermal and instrumental broadening, the latter being primarily due to the applied modulation voltage. With a superconducting Pb counter-electrode, the full-width-at-half-maximum (FWHM) of an IETS peak is given roughly by [ 15 ]... 

Figure 3. Tunneling spectrum of an A l-A I0x-Pb junction with no intentional dopants, for a 2 mV rms modulation voltage at 4.2 K (---) superconducting electrode, ( ---) Pb normal. Inelastic structures that are present even in a junction...

Figure 4. Tunneling characteristics of an Al-AlOx-4-pyridine-COOH-Ag junction run at 1.4 K with a 1 mV modulation voltage, (a) Modulation voltage Vu across the junction for a constant modulation current Iu. This signal is proportional to the dynamic resistance of the sample, (b) Second harmonic signal, proportional to d2V/dI2. (c) Numerically obtained normalized second derivative signal G , dG/ dfeVJ, which is more closely related to the molecular vibrational density of states, (d) Normalized G0 dG/d(eVJ with the smooth elastic background subtracted out...

Observed lineshapes in IETS are further modified by the finite modulation voltages used. We can write the second harmonic current signal at a bias voltage Vq for a given non-linear I-V characteristic as (10) ... 

Fig. 6 shows that for a superconducting electrode the instrumental linewidths are dominated by modulation broadening for modulation voltages greater than 0.5 mV. 

High sensitivity, on the other hand, can be achieved in IETS by using larger modulation voltages. At 2 mV r.m.s. modulation the signal to noise ratio for a... 

Figure 6. Full width at half-maximum of the IETS spectral lines, for an infinitely narrow vibrational density of states, vs. modulation voltage, for two temperatures, and for the counter-electrode (--------) normal or (---) superconducting...

Zhu Y, Ikeda SR (1993) Adenosine modulates voltage-gated Ca2+ channels in adult rat sympathetic neurons. J Neurophysiol 70 610-20... 

Figure 6. Superconducting gap minima (left panel) and phonon structure (right panel) in the spectra of thin film MgE>2-Ag PCs with different resistances at T = 4.2K, B = 0 with Ro=45, 43, and 111 fi for curves 1,2 and 3, respectively. The modulation voltage Vl when measuring the Vh signal is 3.31, 2.78, and 2.5 mV, for curves 1,2 and 3, respectively. The numbers of curves in (b) are the same as in (a). The curves in (a) are offset for clarity. After Yanson et al. [17],...

The measurements were obtained in the frequency range from 100 Hz to 1MHz with the help of a Hewlett Packard impedance analyzer applying a constant bias voltage of 0 V and a modulating voltage of 500 mV [133], Then, the real (Zr) and imaginary (/,) parts of the complex impedance were calculated from the measured impedance. 

The current-voltage characteristics for the electron gun with the prototype (Fig. 2d) and the new (Fig. 2b) CMU design were measured. As one can see, at the anode voltage +10 kV (an operation mode for the cathodoluminescent lamps) the maximum value of the modulator voltage is 1200-1300 V (at the cathode current 100 pA). 

Figure 3. Comparison of experimental (upper panel) and calculated (lower panel) phonon structures in point-contact spectra of MgB2. The contact axis is oriented along the c-axis. The normal state resistances are given for each curve. In the experimental panel the upper curve corresponds to the ordinate scale, and the other two are shifted down for clarity. T = 4.2 K. In the theoretical (lower) panel three transport regimes are illustrated on the same scale as in the experimental graph. Here, the lower curve corresponds to the ordinate scale, the other two are shifted up for clarity. The 7r-band EPI function (dashed curve) [15] is shifted to higher voltages by A,r = 2.4 meV. The modulation voltage is taken equal to 3 mV.

Modulates voltage-sensitive sodium channels by an unknown mechanism... 

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