Voltage criteria

Biventricular hypertrophy. Voltage criteria for LVH found in frontal plane with tall R waves in lead VI Athletes heart , physiological LVH... 

The S wave in lead Vi is added to the R wave in Vg. If the sum is greater than or equal to 35 mm then the voltage criteria for LVH is met. The other method that can be used involves the limb leads 1 and aVL. If a QRS complex exceeds 20 mm (4 large boxes) then the voltage criteria for LVH can be seen using just the Umb leads. 

When recording findings on the ECG it is good practice to write something like voltage criteria for LVH met instead of LVH becanse only a cardiac echo can truly diagnose LVH. 

It is possible to have enlargement of both ventricles, termed biventricular hypertrophy. This can be difficult to spot as the two may cancel each other out to some degree, and the ECG may appear normal. Biventricular hypertrophy may be present if the voltage criteria for LVH is present in limb leads, with tall R waves in lead Vi (Fig. 5.14). 

Figure 5.15 demonstrates the appearance of physiological LVH or Athletes heart as it is sometimes known. Voltage criteria for LVH exists, there are no ST segment or T wave changes or coexistent pathology present. 

Q3. Voltage criteria for Left Ventricular Hypertrophy is found by... 

Q4. The voltage criteria for Left Ventricular Hypertrophy in the precordial leads is said to be... 

A report published by NACE IntemationaP gives additional guidelines about the nature of information that should be supplied by the pipeline operator and by the contractor. A most important consideration in the potential readings is the IR, or ohmic drop error, that is included in the potential measurements when a CP system is operational. As discussed earlier, the voltage criteria for protection against corrosion are based on the potential of the pipeline at the interface... 

Figure 11 Voltage (in percent of full scale) vs current at 7 Tesla magnetic field for a commercial low temperature superconductor using a voltage criterion of different values to indicate the importance of specifying the criterion. Ref. 30.

For each vortex state a specific resistivity-current relation exists, as schematically shown in Fig. 4.2-20. A linear relation occurs for the flux flow regime only. Therefore a voltage criterion for the critical current has to be defined. The one generally used is 1 xV cm . Extensive reviews of the structure and behavior of vortices in high-7i superconductors are given in [2.19,20]. 

When the voltage criterion for LVH exists in adults under the age of 40, this may be a normal variant and not a pathological change. Tall R waves may be found as a normal variant in ... 

This criterion is derived from the fact that the free corrosion potential in soil is generally I/cu Cuso4 -0-55 V. Ohmic voltage drop and protective surface films are not taken into consideration. According to the information in Chapter 4, a maximum corrosion rate for uniform corrosion in soil of 0.1 mm a can be assumed. This corresponds to a current density of 0.1 A m l In Fig. 2-9, the corrosion current density for steel without surface film changes by a factor of 10 with a reduction in potential of about 70 mV. To reduce it to 1 jum a (0.14 V would be necessary. The same level would be available for an ohmic voltage drop. With surfaces covered with films, corrosion at the rest potential and the potential dependence of corrosion in comparison with act contrary to each other so that qualitatively the situation remains the same. More relevant is... 

Additional individual anodes must be installed at points on the protected object where a sufficiently negative pipe/soil potential cannot be achieved. Since usually only the voltage cone is of interest, the place of installation does not depend on the specific soil resistivity. Coke backfill is not necessary, and the place of installation is determined by the local circumstances. Individual horizontal anodes are conveniently installed parallel to the pipeline at the depth of the pipe axis. The voltage, length and distance of the anodes from the protected object are chosen according to Section 9.1 so that criterion No. 6 or No. 7 in Table 3-3 is fulfilled. 

A key criterion for selection of a solvent for electrochemical studies is the electrochemical stability of the solvent [12]. This is most clearly manifested by the range of voltages over which the solvent is electrochemically inert. This useful electrochemical potential window depends on the oxidative and reductive stability of the solvent. In the case of ionic liquids, the potential window depends primarily on the resistance of the cation to reduction and the resistance of the anion to oxidation. (A notable exception to this is in the acidic chloroaluminate ionic liquids, where the reduction of the heptachloroaluminate species [Al2Cl7] is the limiting cathodic process). In addition, the presence of impurities can play an important role in limiting the potential windows of ionic liquids. 

The proof of protection is more difficult to establish in this case for two reasons. First, the object is to restore passivity to the rebar and not to render it virtually immune to corrosion. Second, it is difficult to measure the true electrode potential of rebars under these conditions. This is because the cathodic-protection current flowing through the concrete produces a voltage error in the measurements made (see below). For this reason it has been found convenient to use a potential decay technique to assess protection rather than a direct potential measurement. Thus a 100 mV decay of polarisation in 4 h once current has been interrupted has been adopted as the criterion for adequate protection. It will be seen that this proposal does not differ substantially from the decay criterion included in Table 10.3 and recommended by NACE for assessing the full protection of steel in other environments. Of course, in this case the cathodic polarisation is intended to inhibit pit growth and restore passivity, not to establish effective immunity. 

As pointed out previously, the value of the standard cell voltage, E°, is a measure of the spontaneity of a cell reaction. In Chapter 17, we showed that the standard free energy change, AG°, is a general criterion for reaction spontaneity. As you might suppose, these two quantities have a simple relation to one another and to the equilibrium constant, K, for the cell reaction. 

In summary, we say the voltage of a cell is the same as a cell s emf if determined at zero current. From Faraday s laws of electrolysis, this criterion implies that none of the compositions within the cell can change. In other words, a cell emf is an equilibrium quantity. 

The thermodynamic criterion for spontaneity (feasibility) of a chemical and electrochemical reaction is that the change in free energy, AG have a negative value. Free-energy change in an oxidation-reduction reaction can be calculated from knowledge of the cell voltage ... 

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