Molecular view of the isothermal transformation of a stable glass to a liquid

We have used neutron reflectivity to measure translational motion on the nanometer length scale in exceptionally stable glasses of tris(naphthylbenzene). These glasses are prepared by vapor deposition onto a substrate held somewhat below the glass transition temperature (T(g) = 342 K). When the most stable samples are annealed at 345 K, no translational motion is observed on the 12 nm length scale for over 10,000 s and full mixing requires more than 60,000 s. For comparison, the equilibrium supercooled liquid mixes in 1000 s at this temperature and on this length scale. These measurements provide insight into the mechanism by which a stable glass transforms into a liquid. "Melting" of the stable glass appears to occur by the growth of liquid regions into the surrounding glassy matrix, perhaps by a surface-initiated growth process. At 345 K, translational motion in the stable glass is at least 100 times slower than motion in the supercooled liquid.     

Experimental measurements of atmospheric neutrinos

This talk reports the latest indications of an anomaly in the measurements of atmospheric neutrinos. New results from Soudan-2 and Super-Kamiokande provide evidence that the ratio of ν_μ to ν_e interactions is not as expected. High energy Super-Kamiokande data indicates the cause is a deficit of upward-going ν_μ, and the zenith angle dependence of the effect is consistent with neutrino oscillations. Upward-going muon measurements by several detectors are discussed, but in total they provide inconclusive evidence for the anomaly.     

Isothermal desorption measurements of self-diffusion in supercooled o-terphenyl

Isothermal desorption of o-terphenyl thin-film bilayers was used to measure self-diffusion coefficients of supercooled o-terphenyl near the glass transition temperature (Tg=243 K). Diffusion coefficients from 10(-15.5) to 10(-12) cm2 s(-1) were obtained between 246 and 265 K. Protio and deuterio o-terphenyl were sequentially vapor deposited, then annealed to simultaneously diffuse and desorb the sample in a vacuum chamber. During the desorption of the bilayer, the concentration of each isotope was detected by a mass spectrometer, which revealed the extent of interfacial broadening. In these experiments, isotopic interdiffusion is indistinguishable from self-diffusion and the measured interfacial broadening is consistent with Fickian diffusion. The samples prepared under several different deposition conditions yielded the same self-diffusion coefficients, indicating that the experiments were conducted in the equilibrium supercooled liquid state.     

A FLUORESCENCE STUDY OF THE BINDING OF HOECHST 33258 and DAPI TO HALOGENATED DNAs

We have studied the time-resolved and the steady-state fluorescence of the DNA groove binders 4',6-diamidino-2-phenylindole (DAPI) and Hoechst 33258 with the double stranded DNAs poly(dA-dU) and poly(dI-dC) and their halogenated analogs, poly(dA-I5dU) and poly(dI-Br5dC). These studies were prompted by earlier observations that steady-state fluorescence of Hoechst 33258 is quenched on binding to halogenated DNAs (presumably due to an intermolecular heavy atom effect involving the halogen atom in the major groove), and recent studies which clearly point to a binding-site in the minor groove of DNA. Measurements of the time resolved fluorescence decay demonstrate that the fluorescence of Hoechst 33258 is quenched on binding to the halogenated DNAs, in agreement with previous observations. However, quenching studies carried out using the free halogenated bases IdUrd and BrdCyd in solution yielded bimolecular rate constants more than one order of magnitude larger than those expected for an intermolecular heavy atom effect. Moreover, the quenching of the Hoechst 33258 fluorescence was accompanied by an accelerated photochemical destruction of Hoechst 33258. We therefore conclude that the fluorescence quenching observed with halogenated DNAs is probably due to a photochemical reaction involving Hoechst 33258, rather than direct contact of Hoechst 33258 with the halogen substituents in the major groove of the DNA. The fluorescence decay measurements however, do provide clear evidence for at least two different modes of binding. Taking into account the alternating sequences used in this study and the possibility of two different conformations for bound dye, at least four different modes of binding are plausible. Our present data do not allow us to distinguish between these alternatives. The time-resolved fluorescence decays and fluorescence quantum yields of DAPI are not affected by the presence of the heavy atom substituents in the DNA major groove. Based on this observation and earlier reports that DAPI binds in one of the DNA grooves, we conclude that the high affinity sites for DAPI on DNA are located in the minor groove.     

Occupational safety and health in nanotechnology and Organisation for Economic Cooperation and Development

The Organization for Economic Cooperation and Development (OECD), an intergovernmental organization, is playing a critical global role in ensuring that emerging technologies, such as nanotechnology, are developed responsibly. This article describes OECD activities around occupational safety and health of nanotechnology and provides state-of-the-science overview resulting from an OECD workshop on exposure assessment and mitigation for nanotechnology workplace.     

Measurement of bumetanide in plasma and urine by high-performance liquid chromatography and application to bumetanide disposition.

A high-performance liquid chromatographic method for the measurement of bumetanide in plasma and urine is described. Following precipitation of proteins with acetonitrile, bumetanide was extracted from plasma or urine on a 1-ml bonded-phase C18 column and eluted with acetonitrile. Piretanide dissolved in methanol was used as the internal standard. A C18 Radial Pak column and fluorescence detection (excitation wavelength 228 nm; emission wavelength 418 nm) were used. The mobile phase consisted of methanol-water-glacial acetic acid (66:34:1, v/v) delivered isocratically at a flow-rate of 1.2 ml/min. The lower limit of detection for this method was 5 ng/ml using 0.2 ml of plasma or urine. Nafcillin, but not other semi-synthetic penicillins, was the only commonly used drug that interfered with this assay. No interference from endogenous compounds was detected. For plasma, the inter-assay coefficients of variation of the method were 7.6 and 4.4% for samples containing 10 and 250 ng/ml bumetanide, respectively. The inter-assay coefficients of variation for urine samples containing 10 and 2000 ng/ml were 8.1 and 5.7%, respectively. The calibration curve was linear over the range 5-2000 ng/ml.     

Cross reactivity between human erythropoietin antibody and horse erythropoietin

Erythropoietin (EPO) is the primary hormone of erythropoiesis. Administration of recombinant human erythropoietin (rhuEPO) to improve racing performance in the horse represents a new form of blood doping, which has been associated with increased mortality. While immunoassay kits have become plentiful, very few commercial hormone assays are made specifically for equine research. There is a strong degree of sequence homology reported for EPO among species, which has allowed antibodies designed for human EPO research to be used to determine EPO concentration in other species. The objective of the present study was to use Western blot analysis to determine whether the antibody to rhuEPO, provided in a commercial radioimmunoassay (RIA) kit, recognizes horse EPO. Western blot analysis of purified rhuEPO and horse plasma was conducted, using the polyclonal goat-antihuman EPO antibody supplied in the Incstar EPO Trac RIA as the primary antibody. Immunoblot analysis revealed a major band at approximately 52 kDa for both rhuEPO and the horse plasma. Our results demonstrate that a human EPO antibody recognizes equine EPO. These findings show that the Incstar EPO Trac RIA hormone assay system can be used to measure equine EPO.