Action on obesity: Comprehensive care for all. Report of a Royal College of Physicians, London, working party

Control tumble Originally published in Optics Letters on 01 September 2015 (ol-40-17-4114

Effects of β-Mercaptoethanol on Quantum Dot Emission Evaluated from Photoluminescence Decays

β-mercaptoethanol (BME) has been used as an “anti-blinking” reagent with quantum dots (QDs), but its exact effects on the luminescence behavior of different QD materials have not been quantified. In this study, the luminescence lifetime decays of aqueous solutions of CdTe QDs solubilized with mercaptopropionic acid (MPA) are measured by time-correlated single photon counting (TCSPC) in the presence of varying concentrations of BME. The decays are fit to a model of radiative recombination and trapping that yields the respective time constants as well as the coefficient of intermittency (blinking). It is found that low concentrations of BME in its thiol form (neutral pH) lead to decreases in average lifetime but increased or constant quantum yields, indicating a higher fraction of radiative QDs than without BME. Correspondingly, the blinking coefficients are greatly reduced in the presence of BME at neutral pH. Higher concentrations of BME reduce emission by creating hole traps, a process that requires several hours after BME addition to manifest. Lifetimes are also reduced by the thiolate form of BME (basic pH) but to a lesser degree than at neutral pH. Strikingly, the blinking coefficients are almost entirely unchanged with BME addition at basic pH. In deoxygenated solutions, quantum yields are decreased rather than increased with BME, confirming that the enhancement results from BME’s antioxidant effects. These results provide a quantitative approach to studying blinking and trapping dynamics using time-resolved decays

Chemotaxis Side Chamber

Brine sample exposed to a right-to-left serine gradient. Data file 2015.03.30 06-14. Data for Fig. 9 A in paper

Brine at -4C

Malene Bay brine kept overnight at -4 C with no additions. File 2015.03.28 08-11. Data for Figure 8D in paper and Video 6

Malene Bay eukaryotes

Malene Bay, unmodified, showing eukaryotes. Data for Fig. 6. Data file 2015.03.25 10-1

Brine at +4 C

Malene Bay brine kept overnight at +4 C with the addition of 1/2 strength 2216 marine medium. File 2015.03.30 05-28. Data for Figures 8F in paper and Video 8

Chemotaxis Middle Chamber

Holograms of Malene Bay brine sample exposed to a bottom-to-top serine gradient (data file 2015.03.30 06-28) Data for Fig. 9 B, C in paper and Video S9

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Schematic and images of the compact, twin-beam digital holographic microscope.

<p>(A) Schematic showing four main elements (discussed in the text): the source, the sample (specimen path is labeled <i>Spec</i>. and reference path is labeled <i>Ref</i>.), the microscope, and the sensor. (B) Solid model of the hardware. The fiber-fed source assembly is at the bottom, and the imaging camera is at the top. The microscope optics, comprised of the two aspheric lenses and the relay lens, are contained within the 300 mm long lens tube. In the laboratory, a three-axis stage between the source the microscope optics provides easy manual manipulation of the specimen under study. (C) Photograph of the field instrument (top case removed). The optical train, electronics, and computer are contained within a waterproof box. (D) Photo of instrument fully enclosed, as used in the field. The arrow indicates where a sample chamber is inserted; the structure pictured is a placeholder only.</p

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