12-lead system

FIGURE 17.44 The 10-20 lead system is the standard for placement of EEC electrodes. 

EEG signals are characterized by their extremely small amplitudes (in the microvolt range). Gold-plated electrodes are placed very securely on the scalp to make a very low-resistance contact. A clinically accepted lead system [17], which includes several electrodes placed uniformly around the head, is called the 10-20 lead system (Figure 26.3b). This comprehensive lead system allows localization of diagnostic features, such as seizure spikes, in the vicinity of the electrode [18]. 

These are first-order systems where the phase of the output (in steady-state) leads the phase of the input. The transfer funetion of a first-order lead system is... 

Fig. 6.10 Bode gain and phase for a first-order lead system.

A phase lead eompensator is different from the first-order lead system given in equation (6.35) and Figure 6.10 beeause it eontains both numerator and denominator first-order transfer funetions. 

There seem to be many binary metallic systems in which there are phases of this sort. In the sodium-lead system there are two such phases. One of them, based on the ideal structure Na3Pb, extends from 27 to 30 atomic percent lead, with its maximum at about 28 atomic percent lead and the other, corresponding to the ideal composition NaPb3, extends from 68 to 72 atomic percent lead, with maximum at about 70 atomic percent. The intensities of X-ray reflection have verified that in the second of these phases sodium atoms occupy the positions 0, 0, 0, and the other three positions in the unit cell are occupied by lead atoms isomorphously replaced to some extent by sodium atoms (Zintl Harder, 1931). These two phases are interesting in that the ranges of stability do not include the pure compounds Na8Pb and NaPb3. 

Barretto, P.M.C., Emanation Characteristics of Terrestrial and Lunar Materials and the Radon-222 Loss Effect on the Uranium-Lead System Discordance, Ph.D. thesis, Rice University, Houston (1973). ... 

Russell WA, Papanastassiou DA, Tombrello TA (1978b) Ca isotope fractionation on the Earth and other solar system materials. Geochim Cosmochim Acta 42 1075-1090 Scharer U, Allegre CJ (1982) Uranium-lead system in fragments of a single zircon grain. Nature 295 585-587... 

Lead systems El Nickel systems Sodium systems Lithium-ion systems... 

Treatment of bis(chloromethylether) 54 with a mixed-manganese/lead system generated a reactive intermediate equivalent to the carbonyl yhde depicted in 55. Intermediate 55 behaved as a 1,3-dipole undergoing cycloaddition with a variety of dipolarophiles including A-tosylaldimines such as 56, resulting in the formation of oxazolidine 57 in 73% yield. 

A significant problem in using the uranium-lead system for age dating is that the system is relatively easily disturbed. However, George Wetherill showed that by using both the... 

Temperature variations in the instrument are a source of error and electrical power dissipation is limited to avoid the effects of self-heating. This is achieved by means of the four lead system shown in Fig 6.25ft. This minimises any effects of variations in temperature on the resistance RCL of the connections between the RTD and the bridge and is used normally with digital thermometers and data acquisition systems where the sensor non-linearity is corrected within the computer software. 

In the absence of interactions in the leads (besides the tunneling) one can derive the following exact expression for the lead-system function ... 

Another clear example is the effect of methyl groups on B-subgroup metals. Table 11 compares stability data for mercury, thallium, and lead systems. There is now an effective reduction of (b)-class character due to the extra ligands CH3- This must be attributed to the lowered electron affinity of the metal orbitals if our discussion is correct. 

Figure 9 incorporates a great deal of information and needs some explanation. As the center portion, the figure uses an adaptation of the diagram of liquidus and separation surfaces of the copper-tin-lead system (15) drawn in our standard representation method and scale. On the left is the portion of the copper-lead equilibrium diagram covering... 

Figure 9. (opposite) Liquidus and separation surfaces of the copper-tin-lead system after Ref, 13. Tne appropriate portions of the phase equilibrium diagrams for Cu-Sn and Cu-Pb appear on the sides of the triangle, ( ), Intersection of the liquidus contours with the liquidus of the binary phase diagrams. One should really picture this as a solid triangular prism viewed from the top the sides of the prism would show the binary phase equilibrium diagrams. 

These two previous series of compounds suggested that large cations forming bronze phases with WO3 would yield, at least over the part of the composition range near to WO3 itself, intergrowth type of structures. So far two further groups have been reported, in the Pb-W-O and Ba-W-0 systems. In the lead system a series of... 

Figure 2. Intensity-voltage (/ - V) curve of "dot + leads" system at the equilibrium electron temperature fcuTe = 0.4 meV, but at a different effective phonon temperature...

Efforts to extend TDDFT in this direction were pioneered by several groups [41, 42]. In the approach of Kurth et al. the full KS Hamiltonian of the lead-molecule-lead system is partitioned in the following fashion ... 

FIGURE 17-13. Drawing showing automatic implantable cardioverter-defibrillators with newer methods of device placement. It shows an endocardial lead system where the leads are placed transvenously without the need for a thoracotomy. The generator is now small enough to be placed in the pectoral region of the chest. (From DiMarco, with permission.)... 

The basic quantities required for describing the coupled molecule-lead system are the one particle electron and the phonon Green functions. Following the steps outlined in Section 14.2, the time development for various superoperators (Heisenberg equations) is (all primed indices should be summed over)... 

IpgL- Pb, 89% contained between 1 and 30pgL and 3% contained >30pgL (IRPTC 1979). Only 1.4% of the tap water from 969 US water supplies contained >50pgL lead. Systems having soft water and pH < 6.5 showed the highest concentrations (US EPA 1980). 

The importance of the lithium-lead system is based on its usefulness as a blanket fluid of fusion reactors, which need lithium as breeding material for tritium. The eutectic with 0.68 wt-% (17 at-%) lithium has a melting point of Fp = 235 °C(508 K),... 

The sodium lead system is important, since NaPb compounds are applied to chemical processes. The intermetallic compound NaPb is fabricated in large amounts as an intermediate for the production of tetra ethyl lead. The Na—Pb phase diagram indicates the formation of several compounds, as shown in Fig. 14. The solubility of lead in liquid sodium is considerably high, the saturated solution contains 3 at- % Pb at 250 °C. The sodium-tin system shows a similar solution and compound formation behaviour. 

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