Spectral Polarimetry Research Articles

Signals for Lorentz violation in electrodynamics

An investigation is performed of the Lorentz-violating electrodynamics extracted from the renormalizable sector of the general Lorentz- and CPT-violating standard-model extension. Among the unconventional properties of radiation arising from Lorentz violation is birefringence of the vacuum. Limits on the dispersion of light produced by galactic and extragalactic objects provide bounds of 3 x 10^{-16} on certain coefficients for Lorentz violation in the photon sector. The comparative spectral polarimetry of light from cosmologically distant sources yields stringent constraints of 2 x 10^{-32}. All remaining coefficients in the photon sector are measurable in high-sensitivity tests involving cavity-stabilized oscillators. Experimental configurations in Earth- and space-based laboratories are considered that involve optical or microwave cavities and that could be implemented using existing technology.

Fibre optic spectral polarimetry for sensing multiple stress-loaded locations along a length of fibre

The authors describe a novel fibre optic sensor detecting multiple stress-loaded locations, where cross-coupling takes place in a length of birefringent single-mode fibre. The information about the cross-coupled locations and the distances between them can be obtained from the modulated spectrum due to the interference between the uncross- and cross-coupled modes along the fibre. In the experiment, the determination of only the cross-coupled locations is demonstrated by the processing of the spectral interferences. The performance principle based on spectral polarimetry is described together with experimental demonstrations. The limitation to the spectral polarimetric technique is also discussed for the view of the sensor use.

Enantiometric enrichment of R(−)-alkan-2-ols using a stereospecific alkylsulphatase

When grown on nutrient broth, Pseudomonas C12B produces two secondary alkyl 2-sulphatases, designated S1 and S2 on the basis of electrophoretic mobility. Although both enzymes are synthesised at the end of the exponential phase in batch culture, the appearance of S1 preceded S2 by a few hours in either fermentor or shake-flask cultures. Thus extracts prepared from cells harvested in the intervening period contained only the S1 enzyme. Because S1 and S2 are stereospecific in hydrolysing S(+)- and R(-)-alkyl 2-sulphates to R(-)- and S(+)-alkan-2-ols respectively, the exclusive presence of S1 was exploited in the enantiomeric enrichment of R(-)-alkan-2-ols. Extracts containing only S1 according to gel zymography, hydrolysed only about one-half of added racemic octyl or undecyl 2-sulphates, as expected. Extraction and analysis of liberated octan-2-ol by spectral polarimetry or high resolution gas chromatography with chiral derivatisation, indicated an enantiomeric excess around 60%.