Magnetic flux, measurement

H, for which J = 0, is the intrinsic coercivity whereas the usual coercivity, for which S = 0, is denoted by H or H. For permanent magnets, the value (BH), the maximum energy product, is an important measure of quaHty. The value (BH), iadicated ia the secoad quadrant of Figure 1, represents the poiat of maximum efficieacy where a givea amouat of magnetic flux is produced by the smallest amouat of material. 

The RF SQUID is formed from a single junction in a superconducting loop, which is inductively coupled to a resonant circuit. This is arranged to drive a current round the loop, so that the voltage across the circuit is a measure of the magnetic flux being measured. 

A rate of transfer of entities, particles, fluids through a given point, surface, or pathway. For example, the different pathways for a particular enzyme-catalyzed reaction will have a different flux through each of those pathways. See also Chemical Flux. 2. A measure of the power associated with a particular quantity. See Radiant Energy Flux Radiant Power. 3. A measure of the strength of a particular field of force (eg., magnetic flux). 

We next observe that cpM is in units of volt-seconds (V s) or kg m 2/ (A s-2) = J/A. From Eq. (12) it can be seen that A8 and the phase factor, , are dimensionless. Therefore we can make the prediction that if the magnetic flux, (pM, is known and the phase factor, magnetic charge density, gm, can be found by the following relation ... 

Figure 5. 31P NMR magnetization transfer measurements of ATP turnover in immobilized yeast cells. A control spectrum is shown in (a). Saturation of the y-phosphate resonance of ATP and transfer of this magnetic label through chemical exchange results in a decrease in the intensity of the P, and sugar phosphate resonances (b). This is most clearly seen in the difference spectrum (a-b). The magnitude of the decrease in the P, resonance can be used to calculate the flux between P, and ATP and, hence, the rate of ATP turnover (see Brindle, 1988a,b).

Brindle, K.M. (1988b). 3IP NMR magnetization transfer measurements of flux between inorganic phosphate and ATP in yeast cells genetically modified to over-produce phosphoglycerate kinase. Biochemistry 27,6187-61%. 

Certain ferromagnetic materials, notably iron, steels, and some ceramics (ferrites), are far more receptive ( lOOx) to magnetic flux than is air. Permeability is a measure of the receptiveness of the material to having magnetic flux set up in it [15],... 

The RF SQUID is based on the AC Josephson effect, uses only one Josephson junction, and is less sensitive than the DC SQUID, but is cheaper and easier to manufacture its SQUID is inductively coupled to a resonant tank circuit. Depending on the external magnetic field, as the SQUID operates in the resistive mode, the effective inductance of the tank circuit changes, thus changing the resonant frequency of the tank circuit. These frequency measurements can be easily done, and thus the losses that appear as the voltage across the load resistor in the circuit are a periodic function of the applied magnetic flux with a period of 0. 

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