The determination of nitrate in sea water

A heterogeneous reduction method is described for the determination of nitrate in sea water. Nitrate is reduced to nitrite with 91% efficiency by passing the water through a column of amalgamated cadmium filings. The nitrite produced is determined spectrophotometrically by the method of BENDSCHNEIDER and ROBINSON. The method has a coefficient of variation of ca. 2% and is free from salt error. Temperature in the range o°–35° has no effect on the reduction. Interference from nitrite is discussed and a method is described for its destruction if necessary. Sulphide does not interfere.     

Neutron spectra at 0° from (p,n) reactions on 9Be, 12C,and 27Al at 647 and 800 MeV

The measured cross sections show a narrow high-energy peak (20–30 MeV/cFWHM) and a broad bump at lower momenta associated with pion production. Comparison is made to an intranuclear cascade calculation.     

Microscale functional group analysis of marine and sedimentary humic substances

Methods are described for the microscale analysis of aquatic and sedimentary humic substances for several oxygen-containing functional groups including total acidity, carboxylic and phenolic hydroxyl groups, quinone groups and hydroxamate linkages. Coefficients of variation of the methods range from 4.9 to 12.9%.     

Density functional modelling of silicate and aluminosilicate dimerisation solution chemistry

Common throughout sol-gel chemistry, including zeolite synthesis, aluminosilicate glass formation and geopolymerisation, is the process of inorganic oxide polymerisation and deprotonation. In this investigation, some of the fundamental reactions occurring during zeolite synthesis and geopolymerisation at high pH are investigated using density functional theory (DFT), and are compared with: (i) existing values reported in the literature, and (ii) new and previously published DFT-derived data for similar silicate reactions at near-neutral pH. From the results it is seen that the energetics of deprotonation and dimerisation reactions depend greatly on the pH value, and these results correlate well with existing experimental values and trends. Hence, this investigation exemplifies that an accurate replication of the solution environment is crucial for obtaining useful theoretical results for species dissolved in non-ideal environments.     

ESR Detection of Triplet States in Rare Earth Chelates

Abstract

Energy transfer from ligand molecule to ion in rare earth chelates has been assumed to involve a molecular triplet state. ^1,2 These triplet states manifest themselves optically as long-lived T_{π, π? →S}π,π emission if the lowest resonance level of the ion is of higher energy than the molecular triplet. ³ If the resonance level lies below the triplet, longlived emission is absent or severely reduced in intensity. ^4,5     

Differential etching of chalcogenides for infrared photonic waveguide structures

Chemical etching rates for two different chalcogenide glass compositions, As₄₀S₆₀ and As₂₄S₃₈Se₃₈, were studied using sodium hydroxide based etchant solutions. Etching was performed using a variation of standard photolithographic masking and wet-etching techniques. Variations in etch rate with NaOH concentration and glass composition were observed. The depth of etch was characterized using an optical profilometer. Etch rate differences as large as three orders of magnitude between these two glasses were observed at low NaOH concentration (0.053 M). We present a single variable etch rate curve of etch depth per time (nm/s) versus NaOH overall solution concentration (in M) for these two different chalcogenide glasses. This technology shows promise for fabricating photonic structures and has potential applications in fabricating novel photonic bandgap structures that will function in the long-wave infrared (LWIR) regime.     

Reduced occupancy of the deeply bound 0d(5/2) neutron state in 32Ar

The 9Be(32Ar, 31Ar)X reaction, leading to the 5/2+ ground state of a nucleus at the proton drip line, has a cross section of 10.4(13) mb at a beam energy of 65.1 MeV/nucleon. This translates into a spectroscopic factor that is only 24(3)% of that predicted by the many-body shell-model theory. We introduce refinements to the eikonal reaction theory used to extract the spectroscopic factor to clarify that this very strong reduction represents an effect of nuclear structure. We suggest that it reflects correlation effects linked to the high neutron separation energy (22.0 MeV) for this state.