Standard small targets for calibrating underwater sonars

Ping-pong balls form convenient reference targets for underwater sonars. Theoretical and experimental studies have confirmed that the acoustic target strength of such a ball can be predicted to within about ±·58 dB over a wide range of frequencies, even down to frequencies at which the wavelength in water exceeds the radius of the ball. Computed and experimental results are compared.     

A bivariate strong law of large numbers

Probability Theory and Related Fields -     

Observation of a free radical during the photolysis of phenyliodoacetylene

An ESR spectrum observed during the photolysis of phenyliodoacetylene indicates the formation of a π-radical. It is suggested that a crossing of α- and π-levels occurs in the phenylethynyl radical.     

Preparation and properties of tetramethyl-dipicrylamine

Tetramethyldipicrylamine has been synthesised. It gives precipitates with ammonium, potassium, rubidium and caesium ions, that vary widely in crystalline form and offer a possibility of qualitative usage in chemical microscopy. The potassium salt is of sufficiently low solubility to be of analytical interest.     

The reduction of camera fan noise in a photoprint room

The noise level produced by a fan was reduced by 21 dB(A) by enclosing it in a ‘soundproof box’. The general problems of designing such a box, and, in particular, that of preventing the enclosed fan from overheating, are discussed. The construction of the box is described in detail and its actual performance compared with that theoretically attainable.     

A new reagent for polypeptide synthesis: mu-oxo-bis-(tris-(dimethylamino)-phosphonium)-bis-tetrafluoroborate.

The products 1 and 2 (X = OTs) have been isolated from the reaction between hexamethylphosphortriamide and p-toluene sulfonic anhydride and the latter converted into μ-oxo-bis-[tris-(dimethylamino)-phosphonium]-bis-tetrafluoroborate 2 (X = BF₄). This is a practical reagent for the formation of the peptide link. Where racemisation is possible via oxazolone formation this can be decreased by the addition of 1-hydroxybenzotriazole or N-hydroxysuccinimide. These additives may also increase the efficiency of condensation at glycine and proline residues.     

EXCITED STATES OF FLAVINE COENZYMES-III. FLUORESCENCE AND PHOSPHORESCENCE EMISSIONS

Abstract— Fluorescence and phosphorescence spectra of lumiflavine, riboflavine, FMN and FAD have been measured by continuous and flash excitation techniques. The differences in emission characteristics observed, show that the flavine side-chains afect the singlet-triplet transitions on which chemical and biological activity of flavine systems depend.