The effect of magnetic shaking on nonoriented silicon steel rings
The effect of magnetic shaking on the incremental permeability of nonoriented silicon steel rings was studied. 50H470 silicon steel is a very popular and cheap material, but does not have a high incremental permeability. However, we achieved a value of 27 000 for the target field of 10 Hz, 0.05 A/m, which is comparable to commercial PC permalloy. We also measured the target field, which ranged from 0.05-5 A/m, 1 Hz-1 kHz. Magnetic shaking was effective at 60 Hz is effective at shaking field amplitudes 40-60 A/m, corresponding to a flux density of 0.2-0.6 B/sub s/. We also made ring samples from 50H470 steel plates produced by a nibbling machine and evaluated the effect of stress on their magnetic properties.
Enhancement of Ferromagnetic Shielding against Low-Frequency Magnetic Fields
Experimental data are given to show that the impression of an alternating magnetic field of constant amplitude on a ferromagnetic shield, called shaking, enhances the shielding factor against alternating external magnetic fields. Contrary to expectation the shielding is enhanced against disturbing frequencies both below and above the shaking frequency. It is shown that this effect cannot be explained by a simple model using the harmonics of the shaking induction.
BIOSYNTHESIS OF DAUNORUBICIN GLYCOSIDES: ANALYSIS WITH BLOCKED MUTANTS
ABSTRACT Daunorubicin (daunomycin; NSC 82151) is an anthracycline antibiotic that is useful in the treatment of human leukemias. Several Streptomyces species accumulate higher glycosides of daunorubicin, which can be converted to daunorubicin by simple hydrolysis. We isolated a number of mutants of a daunorubicin glycoside-producing streptomycete, and found that some were deficient in accumulation of daunorubicin glycosides. One such mutant accumulated no detectable anthracyclines, while other mutants accumulated anthracyclines or aglycones that have not been reported before or have been described as co-metabolites of daunorubicin glycosides. Some of these anthracyclines and aglycones were purified and used as substrates in bioconversion experiments with various mutants. The results allowed us to construct a proposed pathway for the biosynthesis of daunorubicin glycosides by this streptomycete. KEYWORDS Anthracycline; daunorubicin; biosynthesis; blocked mutants; biotransformation.