Recovery and recycling of synthetic units in the construction of oligodeoxyribonucleotides on solid supports

Barium salts of protected mono- and dinucleotides have been employed in a scheme for the construction of oligodeoxyribonucleotides on a glass support. The excesses of these synthetic units were recovered simply by precipitation, and reused in subsequent cycles.     

Infrared laser and mass spectrometric analysis of cluster beams: dimer fragmentation due to electron impact

A technique is described in which a combination of mass spectrometric and infrared laser-bolometric detection of molecular beams is used to obtain detailed information concerning tile fragmentation of weakly bound CO dimers due to electron impact.     

Some structural and thermodynamic studies of clathrate hydrates

X-ray and neutron diffraction studies show argon and krypton to preferentially form clathrate hydrates of structure II, rather than structure I as previously assumed; methane and hydrogen sulphide do form structure I. Re-examination of solid-solution thermodynamic theory shows that structure II is basically the more stable; structure I is generally formed only when the guest molecule is in the size range that favours occupancy of the 14-hedral over the 12-hedral cages. For molecules too large to enter the 12-hedra the relative stability of structure II is greatest at 0°C, in agreement with the observed sequence of change of stability of cyclopropane hydrate: I to II at –16° and II to I at 1.5°. Carbon dioxide hydrate is observed to decompose on prolonged standing at 105K in accord with the low-temperature instability predicted by Miller.     

The application of cathodic sputtering to the production of atomic vapours in atomic fluorescence spectroscopy

Cathodic sputtering is used as a source of atomic vapour for the chemical analysis of metals and alloys by atomic fluorescence spectroscopy. The sputtered vapour is produced in a Pyrex glow-discharge chamber which is suitable for the rapid interchange of flat, metallic samples. The discharge operates with a water-cooled cathode specimen and a flow-through gas control system. Linear calibration curves are obtained for the determination of nickel, chromium, copper, manganese and silicon in some iron-base alloy standards. For nickel, chromium and copper, detection limits are of the order of 20 ppm in the iron, and for manganese and silicon about 70 and 400 ppm respectively. The reproducibility of the fluorescence measurements is about ±1%. The system can be readily adapted to provide simultaneous multi-element analysis.     

Anomalous Defect/Impurity Dominated Dielectric Behaviour of Lauric Acid in the Solid Phase

The dieiectric permittivity and loss of solid lauric acid (C₁₁H₂₃COOH) at. audio and radio frequencies are reported for the temperature range from 1.5K to near the melting point No features attributable to confirsurational interchange within the acid-dimer groups are observed. The peculiarities of the data are discussed in terms of the liquid-liKe regions associated with impurity and defect centres.