Single-mode approximation, fractional

A further consequence of the Gaussian approximation is a simple and accurate description of power loss at junctions between single-mode fibers. In practice, junctions are imperfect because of (a) mismatches between fibers, (b) tilts and (c) offsets, as illustrated in Fig. 20-3. If the incident, fundamental-mode fields of the fiber for z < 0 are described by the Gaussian approximation and have spot size Ps, i.e. Fo(r) = exp( — r /2pf), then each junction imperfection can be regarded as a Gaussian beam incident on the fiber in z > 0. If we also use the Gaussian approximation for the latter, as described above, the fractional... 

Smaller values of are obtained for interferometers operated in a double-beam mode, since the moveable mirror must be left stationary for a fraction of the cycle time to allow the detector to stabilize each time the beam is switched from the sample to the reference position. With an optical null grating spectrometer the chopper is used not only to modulate the beam but also to alternate the beam between sample and reference channels. Thus, it takes approximately the same time to measure a transmittance spectrum using a double beam optical null spectrometer as it takes to measure a single-beam spectrum with the same S/R. Hence, for this type of spectrometer may be assigned a value of 2. 

The lactol product target (RT 5.23-5.48 min) peak and impurity A target (RT 4.48-4.70 min) peak were collected via forced time window mode. Fraction dry downtime of MeOH solvent took 1 h with 6 mg of lactol product and 8 mg of impurity A material recovered for NMR analysis. Isolation turnaround time was only 3 h with less than 2 in CO2 and MeOH solvent costs. Impurity A purity was determined to be approximately 95% and subsequently used as a sample source for FT-MS and NMR. The lactol fraction purity was 74% with a single impurity observed. As a result of the purification process impurity A was observed growing into the lactol sample. Indicating that the compound was chemically labile in the solution conditions used for the isolation. Therefore, a semipreparative NP-LC method using 2-propanol and hexane was developed for the... 

---