Transition from a single-ion to a collective diffusion mechanism in alkali borate glasses

Two distinct regions of the dc conductivity and its temperature dependence as a function of the mol fraction of alkali oxides, X, are observed in Na- and Li-borate glasses. At low alkali contents the dc conductivity σ_dc increases only moderately with X. However, at higher alkali contents, log σ_dc increases linearly and the activation enthalpy ΔH of σ_dc × T decreases linearly with log X, i.e. the dc conductivity reveals an effective power-law behavior. The transition between low alkali and high alkali behavior takes place at X ≈ 0.08 for Na-borate and at X ≈ 0.09 for Li-borate glasses. This behavior suggests that the diffusion mechanism changes at these alkali contents. The results are discussed in terms of ion separations and the transition from a single-ion jump to a collective diffusion mechanism. The vanishing of the mixed-alkali peak in Na–Rb borate and alumino-germanate glasses at sodium contents similar to that observed for the change in slope of σ_dc(X) in this work suggests that both phenomena share the same origin.     

Spectrophotometric determination of sulfite with soluble mercury(II) compounds

Sulfite ion reacts with mercury(II) ion in acid solution to form the mercury(I) ion. The reaction is rapid and quantitative. The mercury(I) ion absorbs at 237 nm with a molar

5. Beer's law Data for Sulfite Complexes of Covalent Mercury(II) Compounds

SO2 (ppm)	?HgCl2a	?HgBr2	?Hg(Ac)2b	?Hg(SCN)2
2.0	12,500	10,000	10,000	9,200
4.0	12,500	11,500	10,000	9,000
6.0	12,500	11,500	10,000	9,200
8.0	12,000	11,000	10,500	9,800

a

Molar absorptivity based on sulfite ion at 230 nm. Solution was 6.86 buffer.

b

Mercuric acetate solutions seemed to be somewhat unstable. absorptivity of about 25,000. The absorbance is linear over a range of approximately 0.5–5.0 ppm as SO₂. Covalent mercury(II) compounds form a complex with sulfite, Hg(SO₃)₂^2?, which absorbs at 230 nm and shows a linear response over a range of 1–8 ppm as SO₂.

     

Radiation grafting of vinyl monomers to wool. III. Location of the grafted polymer

Studies of properties such as water sorption of grafted wool have shown the importance of the location of the polymer in the fiber. Electron microscopy and low-angle x-ray diffraction studies have been used to determine the location of grafted polystyrene in wool. Samples grafted from 15 to 800% (dry weight increase) all exhibit a large increase in contrast in the cell membranes (IR) and nuclear-remnant regions (NR) in the electron micrographs. This is considered to be due in part to an unevenness in mechanical response to sectioning and in part to the deposition of ungrafted homopolymer in IR and NR, particularly at grafts of greater than about 100%. Analysis of the change in the 83 A. equatorial x-ray reflection suggests that most of the grafted polymer resides in the keratinous matrix regions between the microfibrils within the cortical cells. At larger grafts the wool still retains its basic histological character, but the increase in this spacing is no longer proportional to the amount of graft, and the desposition of polymer becomes very inhomogeneous.     

Small angle neutron scattering studies on micellar systems part 1. Ammonium octanoate,ammonium decanoate and ammonium perfluoroocatanoate

Small angle neutron scattering has been used to examine the size and shape of micelles of ammonium octanoate, ammonium decanoate and ammonium perfluoro-octanoate. Ammonium octanoate was found to form micelles with a micellar weight of 1640 and ammonium decanoate with a micellar weight of 12,576; both materials appeared to form spherical micelles. Ammonium perfluoro-octanoate formed micelles with a micellar weight of 17,610. Evidence from the scattering experiments suggested that the micelles were cylindrical and a model for the micelle is proposed.     

SERRS-based enzymatic probes for the detection of protease activity

Measurement of protease activity, for the first time using SERRS as a detection method, is reported herein. Synthetic introduction of phenylalanine to a benzotriazole azo dye allows the SERRS response to be "switched off" and subsequent exposure to protease restores the SERRS response. The substrates exhibit varying reactivity for a range of proteases and allow for in situ, real-time analysis of protease reactivity. A limit of detection for one protease, Subtilisin carlsberg, was investigated and was established to be 50 ng ml-1.     

SERRS immunoassay for quantitative human CRP analysis

SERRS has been used for the first time for the measurement of C-reactive protein (CRP) in an immunoassay. CRP, a biological marker for the diagnosis of infection and inflammation, is quantified in an ELISA using conventional reagents, but the usual colorimetric detection step is replaced by SERRS detection, offering improved sensitivity and potential for multiplexing analysis.     

Detection of 2-chloroethylethyl sulfide on soil particles using ion trap-secondary ion mass spectrometry

2-Chloroethylethyl sulfide (CEES) is used as a simulant for mustard (HD) in a study to develop secondary ion mass spectrometry (SIMS) for rapid, semi-quantitative detection of mustard on soil. Selectivity and sensitivity are markedly improved employing multiple-stage mass spectrometry (MS(n)) using an ion trap SIMS. C(2)H(5)SC(2)H(4)(+) from CEES eliminates C(2)H(4) and H(2)S, which are highly diagnostic. CEES was detectable at 0.0012 monolayer on soil. This corresponds to approximately 15 ppm (mass/mass) for a soil having a surface area of 12 m(2) g(-1). A single analysis could be conducted using only 2 mg of soil in under 5 min.