222RN at Bermuda and Mauna Loa: Local and distant sources

Continuous measurements of atmospheric²²²Rn were made for the past three years by the Environmental Measurements Laboratory (EML) at the Atmosphere/Ocean Chemistry Experiment site located at Tudor Hill, Bermuda and at the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Mauna Loa Observatory. The²²²Rn analyzer is based on the two-filter tube method. At the Bermuda site, monthly median²²²Rn concentration range from 50 to 700 mBq m^–3, and the concentrations vary seasonally, with a maximum in the winter and a minimum in the summer. The concentrations are significantly elevated when local winds traverse the island. At MLO, monthly median²²²Rn concentrations range from 100 mBq m^–3 during the fall months to 400 mBq m^–3 during the spring months. The springtime maximum values correspond to periods of rapid transport in the free troposphere from the Asian continent, corroborated by backward air mass trajectories. The²²²Rn data are also used to help decipher local daily upslope/downslope conditions present at MLO. This study illustrates the value of atmospheric²²²Rn monitoring, when screened through the filter of local meteorology, in studying the transport of continental air to the oceans, as well as the dynamics of local meteorological effects.     

Labile species of Pb, Zn and Cd determined by anodic stripping staircase voltammetry and their toxicity to tetrahymena

The amounts of free ions and labile complexes of Pb, Zn and Cd have been determined in a complex organic growth medium by use of anodic stripping staircase voltammetry, ASSV. It was possible to determine the labile fractions of metals and to obtain good correlation with data on the toxicity of the metals to Tetrahymena when using a specific reduction potential (E(s)) for each element, - 600, - 800 and - 1200 mV vs. SCE for Pb, Zn and Cd, respectively. The labile fractions in the organic growth medium were less than 1% for Pb (Pb precipitated), 15% for Zn (as labile complexes) and 30-40% for Cd (as free ions) for total heavy metal concentrations of 0.5mM-2mM. The toxicity to Tetrahymena decreased in the order Cd Zn Pb. The effect of Pb was greater than predicted by ASSV, probably because Tetrahymena additionally ingests the lead-containing precipitate and therefore is exposed to concentrations of Pb exceeding those of the soluble species found in the medium. The results stress the importance of using different specific reduction potentials when different elements are compared, instead of one potential common to all elements. The use of a fixed potential may lead to erroneous conclusions regarding the concentrations of labile species in solution.     

Construction of orbital angular momentum eigenfunctions for many-particle systems by harmonic projection

Formulas are derived which allow the direct construction of total orbital angular momentum eigenfunctions for many-particle systems without the use of Clebsch–Gordan coefficients. One of the equations is closely analogous to Dirac' identity for the total spin operator. This equation describes the action of L² on a function of the particle coordinates in terms of a class operator of the symmetric group and a "contraction operator." A general projection operator for constructing symmetric eigenfunctions of L² is presented.     

Field desorption mass spectrometry of 1-methylpyridinium salts

Quaternary pyridinium salts were investigated by field desorption, field ionization and electron impact mass spectrometry. Thermal decomposition of the salts under field desorption conditions was found to give very abundant volatile products, identified as the dihydro analogues and the ‘methides’ of the cations. The formation of the volatile compounds, especially those with molecular weights corresponding to those of the (cation ?1), (cation +1) and (cation +13) was studied in detail by deuterium and ¹³C labelling experiments.     

Time-resolved and steady-state fluorescence spectroscopic studies of the human lens with comparison to argpyrimidine,pentosidine and 3-OH-kynurenine

The intrinsic fluorescence from the human lens on excitation in the UV region, referred to as blue lens autofluorescence, increases with age or in the presence of diabetes. The present study reveals that the relative contribution of compounds responsible for the blue autofluorescence appears to be a constant with age. Three potential candidates for the blue fluorescence were also studied with respect to fluorescence spectroscopic properties. These were argpyrimidine and pentosidine, both advanced glycation end products, and 3-hydroxykynurenine (3-OH-kynurenine), a photooxidative derivative of tryptophan. It was shown that the spectral properties of argpyrimidine and pentosidine are compatible with the observed blue fluorescence of the human lens, whereas the fluorescence from 3-OH-kynurenine is negligible.