NATA: 50 years experience with accreditation

 Laboratory accreditation is becoming increasingly accepted around the world as a means of identifying technically competent laboratories. It is also being used as a mechanism for the acceptance of test data both nationally and internationally. The concept and mechanisms of accreditation have been developed over the past 50 years. The first national laboratory accreditation system appeared in Australia in 1947. This organisation, known as the National Association of Testing Authorities (NATA), has since taken a leading role in developing accreditation practices that are now used world-wide in evaluating testing, measurement and calibration laboratories. This paper examines the development of the world's first and largest laboratory accreditation system, and looks at the difficulties and triumphs in gaining acceptance and recognition by government and industry of the benefits of laboratory accreditation. Received: 24 June 1996 Accepted: 25 June 1996     

Growth of InP/InGaAs multiple quantum well structures by chemical beam epitaxy

InP/InGaAs multiple quantum well structures with up to 200 periods have been grown by CBE. These structures exhibit exceptional lateral uniformity, measured as ±1 Å in period, ±13 ppm in lattice mismatch and ±0.5 nm in wavelength across a 2 inch wafer. Good surface morphology, sharp interfaces and excellent growth control have all been demonstrated.     

Gold ultra-microelectrode arrays: application to the steady-state voltammetry of hydroxide ion in aqueous solution.

Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array.     

Measurement of the spin and temperature dependence of ddµ molecule formation rate in solid and liquid deuterium

The ddµ molecule formation rate is experimentally measured for the two hyperfine states of the dµ-atom in the temperature range of 5–30 K. Results are consistent with a preliminary measurement by the TRIUMF group and contradict theoretical predictions. The work has been performed on the JINR phasotron (Dubna).     

Total synthesis of himandravine

[reaction: see text] The first total synthesis of (+)-himandravine (1) is described, starting from (2S,6S)-cis-2-formyl-6-methyl-N-Boc-piperidine (8) in 11 linear steps and 17% overall yield. The key step involves a highly diastereoselective intramolecular Diels-Alder reaction of the key intermediate 5 that contains the entire latent carbon framework and functional group substitution of himandravine.     

Dirhodium(II) tetrakis[methyl 2-oxaazetidine-4-carboxylate]: a chiral dirhodium(II) carboxamidate of exceptional reactivity and selectivity

[formula: see text] A new chiral azetidinone-carboxylate ligand for dirhodium(II) catalysis enhances reactivity toward diazo decomposition and selectivity toward cyclopropanation enabling diazomalonates, vinyldiazoacetates, and aryldiazoacetates to be effectively used with a dirhodium(II) carboxamidate catalyst.     

Self-association of daunomycin antibiotic in various buffer solutions

The self-association of an antitumor antibiotic, daunomycin (DAU), in various buffer solutions, including water-salt solutions, phosphate buffer, HEPES, and TRIS, was studied by 1D and 2D ¹H NMR spectroscopy at 500 MHz. The two-dimensional NOESY spectra and the concentration and temperature dependences of the chemical shifts of antibiotic protons in the solvents studied showed that the self-association parameters of DAU were independent of the type of buffer solutions. The most probable two spatial structures of the dimer of DAU in solution were constructed by the method of molecular mechanics. The mutual orientation of the chromophores was parallel in one structure and antiparallel in the other.