Standardization of the Methylene Blue Reduction Test by the Use of Methylene Blue Thiocyanate.
SINCE the first use of methylene blue reduction as an indicator of bacteriological quality in milk, fluid milk supplies on this continent have undergone notable improvement. Moreover, during this period it has been shown that the inaccuracies in the test increase with increasing reduction times.6' 8, 9 An effort to minimize these inaccuracies is, therefore, worth while. Because of the extensive use of this test in milk control activities, it becomes necessary to duplicate frequently the standard tablets of methylene blue certified by the Commission on Standardization of Biological Stains and recognized by the American Public Health Association in Standard Methods of Milk Analysis.' This duplication involves not only the creation of standards but also the purification or, at least, the determination of purity of the dye. Clark, Cohen, and Gibbs 2 review the difficulty, if not the impossibility, either of purification or of determination of purity of methylene blue chloride, the methylene blue salt used in these tablets.
Quirks of dye nomenclature. 8. Methylene blue, azure and violet
Abstract Methylene blue was synthesized in 1877 and soon found application in medicine, staining for microscopy and as an industrial dye and pigment. An enormous literature has accumulated since its introduction. Early on, it was known that methylene blue could be degraded easily by demethylation; consequently, the purity of commercial samples often was low. Therefore, demethylation products, such as azures and methylene violet, also are considered here. The names and identity of the components, their varying modes of manufacture, analytical methods and their contribution to biological staining are discussed.
Super-resolution of overlapped waves in time and frequency domain in a directional borehole radar measurement
The Multiple Signal Classification (MUSIC) algorithm is modified in order to resolve multiple waves and to estimate reflection points in 3-D space. This algorithm is suitable for directional borehole radar with a circular dipole array antenna. Making use of the spatial frequency difference of acquired array signals, the signals are decorrelated, and the 3-D MUSIC algorithm is applied. The time domain signals of the singlehole array-type borehole radar are used in order to form a measurement vector in the MUSIC algorithm. A computer simulation confirms that the proposed algorithm may estimate the directions of arrival (DOA) for three signals. Applying the proposed algorithm to field experiment data successfully estimates the DOA of a reflected wave from a fracture in rock.